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Brown KA, Anderson C, Reilly L, Sondhi K, Ge Y, Eckhardt LL. Proteomic Analysis of the Functional Inward Rectifier Potassium Channel (Kir) 2.1 Reveals Several Novel Phosphorylation Sites. Biochemistry 2021; 60:3292-3301. [PMID: 34676745 DOI: 10.1021/acs.biochem.1c00555] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Membrane proteins represent a large family of proteins that perform vital physiological roles and represent key drug targets. Despite their importance, bioanalytical methods aiming to comprehensively characterize the post-translational modification (PTM) of membrane proteins remain challenging compared to other classes of proteins in part because of their inherent low expression and hydrophobicity. The inward rectifier potassium channel (Kir) 2.1, an integral membrane protein, is critical for the maintenance of the resting membrane potential and phase-3 repolarization of the cardiac action potential in the heart. The importance of this channel to cardiac physiology is highlighted by the recognition of several sudden arrhythmic death syndromes, Andersen-Tawil and short QT syndromes, which are associated with loss or gain of function mutations in Kir2.1, often triggered by changes in the β-adrenergic tone. Therefore, understanding the PTMs of this channel (particularly β-adrenergic tone-driven phosphorylation) is important for arrhythmia prevention. Here, we developed a proteomic method, integrating both top-down (intact protein) and bottom-up (after enzymatic digestion) proteomic analyses, to characterize the PTMs of recombinant wild-type and mutant Kir2.1, successfully mapping five novel sites of phosphorylation and confirming a sixth site. Our study provides a framework for future work to assess the role of PTMs in regulating Kir2.1 functions.
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Affiliation(s)
- Kyle A Brown
- Department of Surgery, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.,Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Corey Anderson
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Louise Reilly
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Kunal Sondhi
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Ying Ge
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States.,Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States
| | - Lee L Eckhardt
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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2
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Inhibitory Effects of Genistein on Vascular Smooth Muscle Cell Proliferation Induced by Ox-LDL: Role of BKCa Channels. ACTA ACUST UNITED AC 2021; 2020:8895449. [PMID: 33415067 PMCID: PMC7752275 DOI: 10.1155/2020/8895449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 12/04/2020] [Indexed: 11/23/2022]
Abstract
Background Oxidized low-density lipoprotein (Ox-LDL) is a crucial pathogenic factor for vascular diseases, which can induce the proliferation of vascular smooth muscle cells (VSMCs). Genistein is the main component of soybean isoflavone. Genistein has a variety of pharmacological properties in the treatment of vascular diseases and a promising clinical application. Large-conductance calcium-activated potassium (BKCa) channels are the primary type of potassium channels in VSMCs, which regulate various biological functions of VSMCs. However, whether genistein exerts an antiproliferation effect on Ox-LDL-stimulated VSMCs remains unclear. The current study is aimed at elucidating the effect of genistein on the Ox-LDL-stimulated proliferation of VSMCs and its possible molecular mechanism, especially the electrophysiological mechanism related to BKCa channels. Methods Monoculture VSMC was obtained by an acute enzyme-dispersing method. The proliferation of cells was measured by CCK-8, cell cycle, and proliferating cell nuclear antigen (PCNA) expression. The BKCa whole-cell currents were measured by patch-clamp. Results Ox-LDL treatment induced the proliferation of VSMCs, upregulated the BKCa protein expression, and increased the density of BKCa currents, while genistein significantly inhibited these effects caused by Ox-LDL. BKCa channels exerted a regulatory role in the proliferation of VSMCs in response to Ox-LDL. The inhibition of BKCa channels suppressed Ox-LDL-stimulated VSMC proliferation, while the activation of BKCa channels showed the opposite effect. Moreover, genistein suppressed the activity of BKCa, including protein expression and current density in a protein tyrosine kinase- (PTK-) dependent manner. Conclusion This study demonstrated that genistein inhibited the Ox-LDL-mediated proliferation of VSMCs by blocking the cell cycle progression; the possible molecular mechanism may be related to PTK-dependent suppression of BKCa channels. Our results provided novel ideas for the application of genistein in the treatment of vascular diseases and proposed a unique insight into the antiproliferative molecular mechanism of genistein.
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3
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Fusi F, Trezza A, Tramaglino M, Sgaragli G, Saponara S, Spiga O. The beneficial health effects of flavonoids on the cardiovascular system: Focus on K+ channels. Pharmacol Res 2020; 152:104625. [DOI: 10.1016/j.phrs.2019.104625] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/14/2019] [Accepted: 12/31/2019] [Indexed: 01/17/2023]
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4
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Jackson WF. Boosting the signal: Endothelial inward rectifier K + channels. Microcirculation 2018; 24. [PMID: 27652592 DOI: 10.1111/micc.12319] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 09/12/2016] [Indexed: 12/19/2022]
Abstract
Endothelial cells express a diverse array of ion channels including members of the strong inward rectifier family composed of KIR 2 subunits. These two-membrane spanning domain channels are modulated by their lipid environment, and exist in macromolecular signaling complexes with receptors, protein kinases and other ion channels. Inward rectifier K+ channel (KIR ) currents display a region of negative slope conductance at membrane potentials positive to the K+ equilibrium potential that allows outward current through the channels to be activated by membrane hyperpolarization, permitting KIR to amplify hyperpolarization induced by other K+ channels and ion transporters. Increases in extracellular K+ concentration activate KIR allowing them to sense extracellular K+ concentration and transduce this change into membrane hyperpolarization. These properties position KIR to participate in the mechanism of action of hyperpolarizing vasodilators and contribute to cell-cell conduction of hyperpolarization along the wall of microvessels. The expression of KIR in capillaries in electrically active tissues may allow KIR to sense extracellular K+ , contributing to functional hyperemia. Understanding the regulation of expression and function of microvascular endothelial KIR will improve our understanding of the control of blood flow in the microcirculation in health and disease and may provide new targets for the development of therapeutics in the future.
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Affiliation(s)
- William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
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5
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Affiliation(s)
- Nhat-Tu Le
- Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX
| | - Jun-Ichi Abe
- Department of Cardiology, The University of Texas MD Anderson Cancer Center, Houston, TX
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6
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Effects of equol on multiple K+ channels stably expressed in HEK 293 cells. PLoS One 2017; 12:e0183708. [PMID: 28832658 PMCID: PMC5568406 DOI: 10.1371/journal.pone.0183708] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 08/09/2017] [Indexed: 12/11/2022] Open
Abstract
The present study investigated the effects of equol on cardiovascular K+ channel currents. The cardiovascular K+ channel currents were determined in HEK 293 cells stably expressing cloned differential cardiovascular K+ channels with conventional whole-cell patch voltage-clamp technique. We found that equol inhibited hKv1.5 (IC50: 15.3 μM), hKv4.3 (IC50: 29.2 μM and 11.9 μM for hKv4.3 peak current and charge area, respectively), IKs (IC50: 24.7 μM) and IhERG (IC50: 31.6 and 56.5 μM for IhERG.tail and IhERG.step, respectively), but not hKir2.1 current, in a concentration-dependent manner. Interestingly, equol increased BKCa current with an EC50 of 0.1 μM. It had no significant effect on guinea pig ventricular action potentials at concentrations of ≤3 μM. These results demonstrate that equol inhibits several cardiac K+ currents at relatively high concentrations, whereas it increases BKCa current at very low concentrations, suggesting that equol is a safe drug candidate for treating patients with cerebral vascular disorders.
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7
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Wernly B, Gonçalves I, Kiss A, Paar V, Mösenlechner T, Leisch M, Santer D, Motloch LJ, Klein KU, Tretter EV, Kretzschmar D, Podesser B, Jung C, Hoppe UC, Lichtenauer M. Differences in Stem Cell Processing Lead to Distinct Secretomes Secretion-Implications for Differential Results of Previous Clinical Trials of Stem Cell Therapy for Myocardial Infarction. Biotechnol J 2017; 12. [PMID: 28731525 DOI: 10.1002/biot.201600732] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 06/28/2017] [Indexed: 01/04/2023]
Abstract
Stem cell therapy for acute myocardial infarction (AMI) seemed to be a promising therapy, however, large clinical trials brought differential outcome. It has been shown that paracrine effects of secretomes of stem cells rather than cell therapy might play a fundamental role. The present study seeks to compare cell processing protocols of clinical trials and investigate effects of differential cell culture conditions on chemokine secretion and functional effects. Different secretomes are compared regarding IL-8, VEGF, MCP-1, and TNF-alpha secretion. Secretome mediated effects are evaluated on endothelial cell (HUVEC) tube formation and migration. Cardioprotective signaling kinases in human cardiomyocytes are determined by Western immunoblotting. Cells processed according to the REPAIR-AMI protocol secrete significantly higher amounts of IL-8 (487.3 ± 1231.1 vs 9.1 ± 8.2 pg mL-1 ; p < 0.05). REAPIR-AMI supernatants lead to significantly pronounced tube formation and migration on HUVEC and enhance the phosphorylation of Akt, ERK, and CREB. Cell processing conditions have a major impact on the composition of the secretome. The REPAIR-AMI secretome significantly enhances proangiogenic chemokine secretion, angiogenesis, cell migration, and cardioprotective signaling pathways. These results might explain differential outcomes between clinical trials. Optimizing cell processing protocols with special regards to paracrine factors, might open a new therapeutic concept for improving patient outcome.
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Affiliation(s)
- Bernhard Wernly
- Internal Medicine II, Department of Cardiology, Paracelsus Medical University Salzburg, Salzburg, Austria
| | - Inês Gonçalves
- Ludwig Boltzmann Cluster for Cardiovascular Research, Department for Biomedical Research, Medical University Vienna, Vienna, Austria
| | - Attila Kiss
- Ludwig Boltzmann Cluster for Cardiovascular Research, Department for Biomedical Research, Medical University Vienna, Vienna, Austria
| | - Vera Paar
- Internal Medicine II, Department of Cardiology, Paracelsus Medical University Salzburg, Salzburg, Austria
| | - Tobias Mösenlechner
- Internal Medicine II, Department of Cardiology, Paracelsus Medical University Salzburg, Salzburg, Austria
| | - Michael Leisch
- Internal Medicine III, Department of Oncology, Paracelsus Medical University Salzburg, Salzburg, Austria
| | - David Santer
- Ludwig Boltzmann Cluster for Cardiovascular Research, Department for Biomedical Research, Medical University Vienna, Vienna, Austria
| | - Lukas Jaroslaw Motloch
- Internal Medicine II, Department of Cardiology, Paracelsus Medical University Salzburg, Salzburg, Austria
| | - Klaus U Klein
- Department of Anesthesia, General Intensive Care and Pain Management, Medical University of Vienna, Vienna, Austria
| | - Eva V Tretter
- Department of Anesthesia, General Intensive Care and Pain Management, Medical University of Vienna, Vienna, Austria
| | - Daniel Kretzschmar
- Universitätsherzzentrum Thüringen, Clinic of Internal Medicine I, Department of Cardiology, Friedrich Schiller University Jena, Jena, Germany
| | - Bruno Podesser
- Ludwig Boltzmann Cluster for Cardiovascular Research, Department for Biomedical Research, Medical University Vienna, Vienna, Austria
| | - Christian Jung
- Division of Cardiology, Pulmonology, and Vascular Medicine University Duesseldorf, Medical Faculty, Duesseldorf, Germany
| | - Uta C Hoppe
- Internal Medicine II, Department of Cardiology, Paracelsus Medical University Salzburg, Salzburg, Austria
| | - Michael Lichtenauer
- Internal Medicine II, Department of Cardiology, Paracelsus Medical University Salzburg, Salzburg, Austria
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Wang Y, Sun HY, Liu YG, Song Z, She G, Xiao GS, Wang Y, Li GR, Deng XL. Tyrphostin AG556 increases the activity of large conductance Ca 2+ -activated K + channels by inhibiting epidermal growth factor receptor tyrosine kinase. J Cell Mol Med 2017; 21:1826-1834. [PMID: 28294531 PMCID: PMC5571560 DOI: 10.1111/jcmm.13103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Accepted: 12/28/2016] [Indexed: 01/08/2023] Open
Abstract
The present study was designed to investigate whether large conductance Ca2+‐activated K+ (BK) channels were regulated by epidermal growth factor (EGF) receptor (EGFR) tyrosine kinase. BK current and channel tyrosine phosphorylation level were measured in BK‐HEK 293 cells expressing both functional α‐subunits and the auxiliary β1‐subunits using electrophysiology, immunoprecipitation and Western blotting approaches, respectively, and the function of rat cerebral basilar arteries was determined with a wire myography system. We found that BK current in BK‐HEK 293 cells was increased by the broad spectrum protein tyrosine kinase (PTK) inhibitor genistein and the selective EGFR tyrosine kinase inhibitor AG556, one of the known tyrphostin. The effect of genistein or AG556 was antagonized by the protein tyrosine phosphatase (PTP) inhibitor orthovanadate. On the other hand, orthovanadate or EGF decreased BK current, and the effect was counteracted by AG556. The tyrosine phosphorylation level of BK channels (α‐ and β1‐subunits) was increased by EGF and orthovanadate, while decreased by genistein and AG556, and the reduced tyrosine phosphorylation of BK channels by genistein or AG556 was reversed by orthovanadate. Interestingly, AG556 induced a remarkable enhancement of BK current in rat cerebral artery smooth muscle cells and relaxation of pre‐contracted rat cerebral basilar arteries with denuded endothelium, and these effects were antagonized by the BK channel blocker paxilline or orthovanadate. These results demonstrate that tyrosine phosphorylation of BK channels by EGFR kinase decreases the channel activity, and inhibition of EGFR kinase by AG556 enhances the channel activity and dilates rat cerebral basilar arteries.
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Affiliation(s)
- Yan Wang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi, China.,Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Hai-Ying Sun
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Ying-Guang Liu
- Institute of Basic Medical Sciences, Xi'an Medical University, Xi'an, Shaanxi, China
| | - Zheng Song
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi, China
| | - Gang She
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi, China
| | - Guo-Sheng Xiao
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, Fujian, China
| | - Yan Wang
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, Fujian, China
| | - Gui-Rong Li
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.,Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, Fujian, China
| | - Xiu-Ling Deng
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi, China.,Cardiovascular Research Centre, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi, China
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9
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Xiao GS, Zhang YH, Wu W, Sun HY, Wang Y, Li GR. Genistein and tyrphostin AG556 decrease ultra-rapidly activating delayed rectifier K + current of human atria by inhibiting EGF receptor tyrosine kinase. Br J Pharmacol 2017; 174:454-467. [PMID: 28072464 DOI: 10.1111/bph.13710] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 12/16/2016] [Accepted: 01/05/2017] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND AND PURPOSE The ultra-rapidly activating delayed rectifier K+ current IKur (encoded by Kv 1.5 or KCNA5) plays an important role in human atrial repolarization. The present study investigates the regulation of this current by protein tyrosine kinases (PTKs). EXPERIMENTAL APPROACH Whole-cell patch voltage clamp technique and immunoprecipitation and Western blotting analysis were used to investigate whether the PTK inhibitors genistein, tyrphostin AG556 (AG556) and PP2 regulate human atrial IKur and hKv1.5 channels stably expressed in HEK 293 cells. KEY RESULTS Human atrial IKur was decreased by genistein (a broad-spectrum PTK inhibitor) and AG556 (a highly selective EGFR TK inhibitor) in a concentration-dependent manner. Inhibition of IKur induced by 30 μM genistein or 10 μM AG556 was significantly reversed by 1 mM orthovanadate (a protein tyrosine phosphatase inhibitor). Similar results were observed in HEK 293 cells stably expressing hKv 1.5 channels. On the other hand, the Src family kinase inhibitor PP2 (1 μM) slightly enhanced IKur and hKv 1.5 current, and the current increase was also reversed by orthovanadate. Immunoprecipitation and Western blotting analysis showed that genistein, AG556, and PP2 decreased tyrosine phosphorylation of hKv 1.5 channels and that the decrease was countered by orthovanadate. CONCLUSION AND IMPLICATIONS The PTK inhibitors genistein and AG556 decrease human atrial IKur and cloned hKv 1.5 channels by inhibiting EGFR TK, whereas the Src kinase inhibitor PP2 increases IKur and hKv 1.5 current. These results imply that EGFR TK and the soluble Src kinases may have opposite effects on human atrial IKur .
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Affiliation(s)
- Guo-Sheng Xiao
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, Fujian, China
| | - Yan-Hui Zhang
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, Fujian, China.,Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Wei Wu
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Hai-Ying Sun
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Yan Wang
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, Fujian, China
| | - Gui-Rong Li
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, Fujian, China.,Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China
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10
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Fluid flow facilitates inward rectifier K + current by convectively restoring [K +] at the cell membrane surface. Sci Rep 2016; 6:39585. [PMID: 28004830 PMCID: PMC5177964 DOI: 10.1038/srep39585] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 11/24/2016] [Indexed: 01/25/2023] Open
Abstract
The inward rectifier Kir2.1 current (IKir2.1) was reported to be facilitated by fluid flow. However, the mechanism underlying this facilitation remains uncertain. We hypothesized that during K+ influx or efflux, [K+] adjacent to the outer mouth of the Kir2.1 channel might decrease or increase, respectively, compared with the average [K+] of the bulk extracellular solution, and that fluid flow could restore the original [K+] and result in the apparent facilitation of IKir2.1. We recorded the IKir2.1 in RBL-2H3 cells and HEK293T cells that were ectopically over-expressed with Kir2.1 channels by using the whole-cell patch-clamp technique. Fluid-flow application immediately increased the IKir2.1, which was not prevented by either the pretreatment with inhibitors of various protein kinases or the modulation of the cytoskeleton and caveolae. The magnitudes of the increases of IKir2.1 by fluid flow were driving force-dependent. Simulations performed using the Nernst-Planck mass equation indicated that [K+] near the membrane surface fell markedly below the average [K+] of the bulk extracellular solution during K+ influx, and, notably, that fluid flow restored the decreased [K+] at the cell surface in a flow rate-dependent manner. These results support the “convection-regulation hypothesis” and define a novel interpretation of fluid flow-induced modulation of ion channels.
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11
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Masia R, Krause DS, Yellen G. The inward rectifier potassium channel Kir2.1 is expressed in mouse neutrophils from bone marrow and liver. Am J Physiol Cell Physiol 2014; 308:C264-76. [PMID: 25472961 DOI: 10.1152/ajpcell.00176.2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neutrophils are phagocytic cells that play a critical role in innate immunity by destroying bacterial pathogens. Channels belonging to the inward rectifier potassium channel subfamily 2 (Kir2 channels) have been described in other phagocytes (monocytes/macrophages and eosinophils) and in hematopoietic precursors of phagocytes. Their physiological function in these cells remains unclear, but some evidence suggests a role in growth factor-dependent proliferation and development. Expression of functional Kir2 channels has not been definitively demonstrated in mammalian neutrophils. Here, we show by RT-PCR that neutrophils from mouse bone marrow and liver express mRNA for the Kir2 subunit Kir2.1 but not for other subunits (Kir2.2, Kir2.3, and Kir2.4). In electrophysiological experiments, resting (unstimulated) neutrophils from mouse bone marrow and liver exhibit a constitutively active, external K(+)-dependent, strong inwardly rectifying current that constitutes the dominant current. The reversal potential is dependent on the external K(+) concentration in a Nernstian fashion, as expected for a K(+)-selective current. The current is not altered by changes in external or internal pH, and it is blocked by Ba(2+), Cs(+), and the Kir2-selective inhibitor ML133. The single-channel conductance is in agreement with previously reported values for Kir2.1 channels. These properties are characteristic of homomeric Kir2.1 channels. Current density in short-term cultures of bone marrow neutrophils is decreased in the absence of growth factors that are important for neutrophil proliferation [granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF)]. These results demonstrate that mouse neutrophils express functional Kir2.1 channels and suggest that these channels may be important for neutrophil function, possibly in a growth factor-dependent manner.
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Affiliation(s)
- Ricard Masia
- Department of Pathology and Laboratory Medicine, Massachusetts General Hospital, Boston, Massachusetts; and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts
| | - Daniela S Krause
- Department of Pathology and Laboratory Medicine, Massachusetts General Hospital, Boston, Massachusetts; and
| | - Gary Yellen
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts
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12
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Schmitt N, Grunnet M, Olesen SP. Cardiac potassium channel subtypes: new roles in repolarization and arrhythmia. Physiol Rev 2014; 94:609-53. [PMID: 24692356 DOI: 10.1152/physrev.00022.2013] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
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 drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K+ channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure. The underlying posttranscriptional and posttranslational remodeling of the individual K+ channels changes their activity and significance relative to each other, and they must be viewed together to understand their role in keeping a stable heart rhythm, also under menacing conditions like attacks of reentry arrhythmia.
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13
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Leroy MC, Perroud J, Darbellay B, Bernheim L, Konig S. Epidermal growth factor receptor down-regulation triggers human myoblast differentiation. PLoS One 2013; 8:e71770. [PMID: 23967242 PMCID: PMC3744467 DOI: 10.1371/journal.pone.0071770] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 07/09/2013] [Indexed: 12/02/2022] Open
Abstract
Initiation of human myoblast differentiation requires a negative shift (hyperpolarization) of the resting potential of myoblasts that depends on the activation of Kir2.1 potassium channels. These channels are regulated by a tyrosine phosphorylation. Using human primary myoblast culture, we investigated a possible role of various receptor tyrosine kinases in the induction of the differentiation process. We found that Epidermal Growth Factor Receptor (EGFR) is a key regulator of myoblast differentiation. EGFR activity is down-regulated during early human myoblast differentiation, and this event is required for normal differentiation to take place. Furthermore, EGFR silencing in proliferation conditions was able to trigger the differentiation program. This occurs through an increase of Kir2.1 channel activity that, via a rise of store-operated Ca2+ entry, leads to the expression of myogenic transcription factors and muscle specific proteins (Myogenin, Myocyte Enhancer Factor 2 (MEF2), Myosin Heavy Chain (MyHC)). Finally, blocking myoblast cell cycle in proliferation conditions using a cdk4 inhibitor greatly decreased myoblast proliferation but was not able, on its own, to promote myoblast differentiation. Taken together, these results show that EGFR down-regulation is an early event that is required for the induction of myoblast differentiation.
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Affiliation(s)
- Marina C. Leroy
- Department of Basic Neurosciences, University Medical Center, Geneva, Switzerland
| | - Julie Perroud
- Department of Basic Neurosciences, University Medical Center, Geneva, Switzerland
| | - Basile Darbellay
- Department of Clinical Neurosciences, University Hospital, Geneva, Switzerland
| | - Laurent Bernheim
- Department of Basic Neurosciences, University Medical Center, Geneva, Switzerland
| | - Stephane Konig
- Department of Basic Neurosciences, University Medical Center, Geneva, Switzerland
- * E-mail:
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14
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EGFR tyrosine kinase regulates human small-conductance Ca2+-activated K+ (hSKCa1) channels expressed in HEK-293 cells. Biochem J 2013; 452:121-9. [PMID: 23496660 DOI: 10.1042/bj20121324] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
SKCa (small-conductance Ca(2+)-activated K(+)) channels are widely distributed in different tissues, including the brain, pancreatic islets and myocardium and play an important role in controlling electrical activity and cellular functions. However, intracellular signal modulation of SKCa channels is not fully understood. The present study was designed to investigate the potential regulation of hSKCa1 (human SKCa1) channels by PTKs (protein tyrosine kinases) in HEK (human embryonic kidney)-293 cells expressing the hSKCa1 (KCNN1) gene using approaches of whole-cell patch voltage-clamp, immunoprecipitation, Western blotting and mutagenesis. We found that the hSKCa1 current was inhibited by the broad-spectrum PTK inhibitor genistein, the selective EGFR (epidermal growth factor receptor) kinase inhibitors T25 (tyrphostin 25) and AG556 (tyrphostin AG 556), but not by the Src-family kinases inhibitor PP2. The inhibitory effect of these PTK inhibitors was significantly antagonized by the PTP (protein tyrosine phosphatase) inhibitor orthovanadate. The tyrosine phosphorylation level of hSKCa1 channels was reduced by genistein, T25 or AG556. The reduced tyrosine phosphorylation was countered by orthovanadate. Interestingly, the Y109F mutant hSKCa1 channel lost the inhibitory response to T25 or AG556, and showed a dramatic reduction in tyrosine phosphorylation levels and a reduced current density. These results demonstrate the novel information that hSKCa1 channels are inhibited by genistein, T25 and AG556 via EGFR tyrosine kinase inhibition, which is related to the phosphorylation of Tyr(109) in the N-terminus. This effect may affect electrical activity and cellular functions in brain, pancreatic islets and myocardium.
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Zhang YH, Wu W, Sun HY, Deng XL, Cheng LC, Li X, Tse HF, Lau CP, Li GR. Modulation of human cardiac transient outward potassium current by EGFR tyrosine kinase and Src-family kinases. Cardiovasc Res 2011; 93:424-33. [PMID: 22198508 DOI: 10.1093/cvr/cvr347] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
AIMS The human cardiac transient outward K(+) current I(to) (encoded by Kv4.3 or KCND3) plays an important role in phase 1 rapid repolarization of cardiac action potentials in the heart. However, modulation of I(to) by intracellular signal transduction is not fully understood. The present study was therefore designed to determine whether/how human atrial I(to) and hKv4.3 channels stably expressed in HEK 293 cells are regulated by protein tyrosine kinases (PTKs). METHODS AND RESULTS Whole-cell patch voltage-clamp, immunoprecipitation, western blotting, and site-directed mutagenesis approaches were employed in the present study. We found that human atrial I(to) was inhibited by the broad-spectrum PTK inhibitor genistein, the selective epidermal growth factor receptor (EGFR) kinase inhibitor AG556, and the Src-family kinases inhibitor PP2. The inhibitory effect was countered by the protein tyrosine phosphatase inhibitor orthovanadate. In HEK 293 cells stably expressing human KCND3, genistein, AG556, and PP2 significantly reduced the hKv4.3 current, and the reduction was antagonized by orthovanadate. Interestingly, orthovanadate also reversed the reduced tyrosine phosphorylation level of hKv4.3 channels by genistein, AG556, or PP2. Mutagenesis revealed that the hKv4.3 mutant Y136F lost the inhibitory response to AG556, while Y108F lost response to PP2. The double-mutant Y108F-Y136F hKv4.3 channels showed no response to either AG556 or PP2. CONCLUSION Our results demonstrate that human atrial I(to) and cloned hKv4.3 channels are modulated by EGFR kinase via phosphorylation of the Y136 residue and by Src-family kinases via phosphorylation of the Y108 residue; tyrosine phosphorylation of the channel may be involved in regulating cardiac electrophysiology.
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Affiliation(s)
- Yan-Hui Zhang
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, L4-59, Laboratory Block, FMB, 21 Sassoon Road, Pokfulam, Hong Kong, China
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Wu W, Dong MQ, Wu XG, Sun HY, Tse HF, Lau CP, Li GR. Human ether-à-go-go gene potassium channels are regulated by EGFR tyrosine kinase. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:282-9. [PMID: 22061963 DOI: 10.1016/j.bbamcr.2011.10.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 10/21/2011] [Accepted: 10/24/2011] [Indexed: 11/15/2022]
Abstract
Human ether á-go-go gene potassium channels (hEAG1 or Kv10.1) are expressed in brain and various human cancers and play a role in neuronal excitement and tumor progression. However, the functional regulation of hEAG channels by signal transduction is not fully understood. The present study was therefore designed to investigate whether hEAG1 channels are regulated by protein tyrosine kinases (PTKs) in HEK 293 cells stably expressing hEAG1 gene using whole-cell patch voltage-clamp, immunoprecipitation, Western blot, and mutagenesis approaches. We found that the selective epidermal growth factor receptor (EGFR) kinase inhibitor AG556 (10 μM), but not the platelet growth factor receptor (PDGFR) kinase inhibitor AG1295 (10 μM) or the Src-family inhibitor PP2 (10 μM), can inhibit hEAG1 current, and the inhibitory effect can be reversed by the protein tyrosine phosphatase (PTP) inhibitor orthovanadate. Immunoprecipitation and Western blot analysis revealed that tyrosine phosphorylation level of hEAG1 channels was reduced by AG556, and the reduction was significantly countered by orthovanadate. The hEAG1 mutants Y90A, Y344A and Y485A, but not Y376A and Y479A, exhibited reduced response to AG556. Interestingly, the inhibition effect of AG556 was lost in triple mutant hEAG1 channels at Y90, Y344, and Y485 with alanine. These results demonstrate for the first time that hEAG1 channel activity is regulated by EGFR kinase at the tyrosine residues Tyr90, Try344, and Try485. This effect is likely involved in regulating neuronal activity and/or tumor growth.
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Affiliation(s)
- Wei Wu
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China
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