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Logue MJE, Farquhar RE, Eckhoff-Björngard Y, Cheung TT, Devor DC, McDonald FJ, Hamilton KL. The Exocyst Complex is Required for the Trafficking and Delivery of KCa3.1 to the Basolateral Membrane of Polarized Epithelia. Am J Physiol Cell Physiol 2023. [PMID: 37125772 DOI: 10.1152/ajpcell.00374.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Control of the movement of ions and water across epithelia is essential for homeostasis. Changing the number or activity of ion channels at the plasma membrane is a significant regulator of epithelial transport. In polarized epithelia, the intermediate-conductance calcium-activated potassium channel, KCa3.1 is delivered to the basolateral membrane where it generates and maintains the electrochemical gradients required for epithelial transport. The mechanisms that control the delivery of KCa3.1 to the basolateral membrane are still emerging. Herein we investigated the role of the highly conserved tethering complex exocyst. In epithelia, exocyst is involved in the tethering of post-Golgi secretory vesicles with the basolateral membrane, which is required before membrane fusion. In our Fisher rat thyroid cell line that stably expresses KCa3.1, siRNA knockdown of either of the exocyst subunits Sec3, Sec6, or Sec8 significantly decreased KCa3.1-specific current. Additionally, knockdown of exocyst complex subunits significantly reduced the basolateral membrane protein level of KCa3.1. Finally, co-immunoprecipitation experiments, suggest associations between Sec6 and KCa3.1, but not between Sec8 and KCa3.1. Collectively, based on these data and our previous studies, we suggest that components of exocyst complex are crucially important in the tethering of KCa3.1 to the basolateral membrane. After which, SNARE proteins aid in the insertion of KCa3.1-containing vesicles into the basolateral membrane of polarized epithelia.
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Affiliation(s)
- Matthew J E Logue
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Rachel E Farquhar
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Yoakim Eckhoff-Björngard
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Tanya T Cheung
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Daniel C Devor
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Fiona J McDonald
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Kirk L Hamilton
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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Costa ADS, Mortensen P, Hortigon-Vinagre MP, van der Heyden MAG, Burton FL, Gao H, Simitev RD, Smith GL. Electrophysiology of hiPSC-Cardiomyocytes Co-Cultured with HEK Cells Expressing the Inward Rectifier Channel. Int J Mol Sci 2021; 22:6621. [PMID: 34205607 DOI: 10.3390/ijms22126621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/07/2021] [Accepted: 06/11/2021] [Indexed: 11/23/2022] Open
Abstract
The immature electrophysiology of human-induced pluripotent stem cell-derived cardiomyocytes (hiCMs) complicates their use for therapeutic and pharmacological purposes. An insufficient inward rectifying current (IK1) and the presence of a funny current (if) cause spontaneous electrical activity. This study tests the hypothesis that the co-culturing of hiCMs with a human embryonic kidney (HEK) cell-line expressing the Kir2.1 channel (HEK-IK1) can generate an electrical syncytium with an adult-like cardiac electrophysiology. The mechanical activity of co-cultures using different HEK-IK1:hiCM ratios was compared with co-cultures using wildtype (HEK–WT:hiCM) or hiCM alone on days 3–8 after plating. Only ratios of 1:3 and 1:1 showed a significant reduction in spontaneous rate at days 4 and 6, suggesting that IK1 was influencing the electrophysiology. Detailed analysis at day 4 revealed an increased incidence of quiescent wells or sub-areas. Electrical activity showed a decreased action potential duration (APD) at 20% and 50%, but not at 90%, alongside a reduced amplitude of the aggregate AP signal. A computational model of the 1:1 co-culture replicates the electrophysiological effects of HEK–WT. The addition of the IK1 conductance reduced the spontaneous rate and APD20, 50 and 90, and minor variation in the intercellular conductance caused quiescence. In conclusion, a 1:1 co-culture HEK-IK1:hiCM caused changes in electrophysiology and spontaneous activity consistent with the integration of IK1 into the electrical syncytium. However, the additional electrical effects of the HEK cell at 1:1 increased the possibility of electrical quiescence before sufficient IK1 was integrated into the syncytium.
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Ivanova AD, Filatova TS, Abramochkin DV, Atkinson A, Dobrzynski H, Kokaeva ZG, Merzlyak EM, Pustovit KB, Kuzmin VS. Attenuation of inward rectifier potassium current contributes to the α1-adrenergic receptor-induced proarrhythmicity in the caval vein myocardium. Acta Physiol (Oxf) 2021; 231:e13597. [PMID: 33306261 DOI: 10.1111/apha.13597] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 11/19/2020] [Accepted: 12/07/2020] [Indexed: 12/31/2022]
Abstract
AIM This study is aimed at investigation of electrophysiological effects of α1-adrenoreceptor (α1-AR) stimulation in the rat superior vena cava (SVC) myocardium, which is one of the sources of proarrhythmic activity. METHODS α1-ARs agonists (phenylephrine-PHE or norepinephrine in presence of atenolol-NE + ATL) were applied to SVC and atrial tissue preparations or isolated cardiomyocytes, which were examined using optical mapping, glass microelectrodes or whole-cell patch clamp. α1-ARs distribution was evaluated using immunofluorescence. Kir2.X mRNA and protein level were estimated using RT-PCR and Western blotting. RESULTS PHE or NE + ATL application caused a significant suppression of the conduction velocity (CV) of excitation and inexcitability in SVC, an increase in the duration of electrically evoked action potentials (APs), a decrease in the maximum upstroke velocity (dV/dtmax ) and depolarization of the resting membrane potential (RMP) in SVC to a greater extent than in atria. The effects induced by α1-ARs activation in SVC were attenuated by protein kinase C inhibition (PKC). The whole-cell patch clamp revealed PHE-induced suppression of outward component of IK1 inward rectifier current in isolated SVC, but not atrial myocytes. These effects can be mediated by α1A subtype of α-ARs found in abundance in rat SVC. The basal IK1 level in SVC was much lower than in atria as a result of the weaker expression of Kir2.2 channels. CONCLUSION Therefore, the reduced density of IK1 in rat SVC cardiomyocytes and sensitivity of this current to α1A-AR stimulation via PKC-dependent pathways might lead to proarrhythmic conduction in SVC myocardium by inducing RMP depolarization, AP prolongation, CV and dV/dtmax decrease.
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Affiliation(s)
- Alexandra D. Ivanova
- Department of Human and Animal Physiology Lomonosov Moscow State University Moscow Russia
| | - Tatiana S. Filatova
- Department of Human and Animal Physiology Lomonosov Moscow State University Moscow Russia
- Department of Physiology Pirogov Russian National Research Medical University Moscow Russia
| | - Denis V. Abramochkin
- Department of Human and Animal Physiology Lomonosov Moscow State University Moscow Russia
- Department of Physiology Pirogov Russian National Research Medical University Moscow Russia
- Laboratory of Cardiac Electrophysiology National Medical Research Center for Cardiology Moscow Russia
| | - Andrew Atkinson
- Faculty of Biology, Medicine and Health University of Manchester Manchester UK
| | - Halina Dobrzynski
- Faculty of Biology, Medicine and Health University of Manchester Manchester UK
- Heart Embryology and Anatomy Research Team Department of Anatomy Jagiellonian University Medical College Cracow Poland
| | - Zarema G. Kokaeva
- Department of Human and Animal Physiology Lomonosov Moscow State University Moscow Russia
| | - Ekaterina M. Merzlyak
- Shemiakin‐Ovchinnikov Institute of Bioorganic Chemistry Russian Academy of Science Moscow Russia
| | - Ksenia B. Pustovit
- Department of Human and Animal Physiology Lomonosov Moscow State University Moscow Russia
| | - Vladislav S. Kuzmin
- Department of Human and Animal Physiology Lomonosov Moscow State University Moscow Russia
- Department of Physiology Pirogov Russian National Research Medical University Moscow Russia
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van der Schoor L, van Hattum EJ, de Wilde SM, Harlianto NI, van Weert AJ, Bloothooft M, van der Heyden MAG. Towards the Development of AgoKirs: New Pharmacological Activators to Study K ir2.x Channel and Target Cardiac Disease. Int J Mol Sci 2020; 21:E5746. [PMID: 32796537 DOI: 10.3390/ijms21165746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/05/2020] [Accepted: 08/06/2020] [Indexed: 12/15/2022] Open
Abstract
Inward rectifier potassium ion channels (IK1-channels) of the Kir2.x family are responsible for maintaining a stable negative resting membrane potential in excitable cells, but also play a role in processes of non-excitable tissues, such as bone development. IK1-channel loss-of-function, either congenital or acquired, has been associated with cardiac disease. Currently, basic research and specific treatment are hindered by the absence of specific and efficient Kir2.x channel activators. However, twelve different compounds, including approved drugs, show off-target IK1 activation. Therefore, these compounds contain valuable information towards the development of agonists of Kir channels, AgoKirs. We reviewed the mechanism of IK1 channel activation of these compounds, which can be classified as direct or indirect activators. Subsequently, we examined the most viable starting points for rationalized drug development and possible safety concerns with emphasis on cardiac and skeletal muscle adverse effects of AgoKirs. Finally, the potential value of AgoKirs is discussed in view of the current clinical applications of potentiators and activators in cystic fibrosis therapy.
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5
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Yuan D, Tan C, Yao JM, Li D, Huang SH, Wu Z. [Effects of Continuous Training on the Induction of Atrial Fibrillation in a Rabbit Model]. Sichuan Da Xue Xue Bao Yi Xue Ban 2020; 51:213-218. [PMID: 32220190 DOI: 10.12182/20200360203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Objective This study was aimed to assess mechanisms underlying continuous training induced atrial fibrillation (AF) in an animal model. Methods Healthy New Zealand rabbits were divided into three groups ( n=12 each): control group (C), moderate intensity group (M), and high intensity group (H). The intensity of continuous training was adjusted according to the treadmill speed. After 12 weeks of training, with a Langendorff perfusion system, AF was induced by S1S2 stimulation and the incidence was recorded. Changes in atrial kir2.1, kir2.2, type Ⅰ and Ⅲ collagen protein mRNA expressions were assessed by quantitative real-time PCR. Masson staining was used to assess the extracellular collagen volume fraction (CVF) . Results After 12 weeks, comparing with group C, groups M and H had greater ( P<0.05): CVF, incidence of AF ( P<0.05, also between Groups H and M), and atrial inward rectifier potassium current/channel (IK 1) . In Group H, kir2.1, kir2.2, type Ⅰ and Ⅲ collagen protein mRNA expressions in the left atrium were increased ( P<0.05, compared with Groups C and M). Conclusion Long-term and high-intensity treadmill running could increase AF incidence in rabbits.
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Affiliation(s)
- Dou Yuan
- Department of Cardiovascular Surgery, Chengdu Shang Jin Nan Fu Hospital, West China Hospital, Sichuan University, Chengdu 611743, China
| | - Chen Tan
- Department of Cardiology, Hebei Yan Da Hospital, Sanhe 065200, China
| | - Jian-Min Yao
- Department of Cardiovascular Surgery, Second Hospital of Shanxi Medical University, Taiyuan 030000, China
| | - Dan Li
- Department of Ultrasound, PLA General Hopsital, Beijing 100000, China
| | - Si-Hui Huang
- Department of Cardiology, Peking University First Hospital, Beijing 100000, China
| | - Zhong Wu
- Department of Cardiovascular Surgery, West China Hospital, Sichuan University, Chengdu 610041, China
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Tobón C, Palacio LC, Chidipi B, Slough DP, Tran T, Tran N, Reiser M, Lin YS, Herweg B, Sayad D, Saiz J, Noujaim S. The Antimalarial Chloroquine Reduces the Burden of Persistent Atrial Fibrillation. Front Pharmacol 2019; 10:1392. [PMID: 31827438 PMCID: PMC6890839 DOI: 10.3389/fphar.2019.01392] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 10/31/2019] [Indexed: 12/31/2022] Open
Abstract
In clinical practice, reducing the burden of persistent atrial fibrillation by pharmacological means is challenging. We explored if blocking the background and the acetylcholine-activated inward rectifier potassium currents (IK1 and IKACh) could be antiarrhythmic in persistent atrial fibrillation. We thus tested the hypothesis that blocking IK1 and IKACh with chloroquine decreases the burden of persistent atrial fibrillation. We used patch clamp to determine the IC50 of IK1 and IKACh block by chloroquine and molecular modeling to simulate the interaction between chloroquine and Kir2.1 and Kir3.1, the molecular correlates of IK1 and IKACh. We then tested, as a proof of concept, if oral chloroquine administration to a patient with persistent atrial fibrillation can decrease the arrhythmia burden. We also simulated the effects of chloroquine in a 3D model of human atria with persistent atrial fibrillation. In patch clamp the IC50 of IK1 block by chloroquine was similar to that of IKACh. A 14-day regimen of oral chloroquine significantly decreased the burden of persistent atrial fibrillation in a patient. Mathematical simulations of persistent atrial fibrillation in a 3D model of human atria suggested that chloroquine prolonged the action potential duration, leading to failure of reentrant excitation, and the subsequent termination of the arrhythmia. The combined block of IK1 and IKACh can be a targeted therapeutic strategy for persistent atrial fibrillation.
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Affiliation(s)
| | | | - Bojjibabu Chidipi
- Molecular Pharmacology and Physiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Diana P Slough
- Department of Chemistry, Tufts University, Medford, MA, United States
| | - Thanh Tran
- Cardiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Nhi Tran
- Cardiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Michelle Reiser
- Molecular Pharmacology and Physiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Yu-Shan Lin
- Department of Chemistry, Tufts University, Medford, MA, United States
| | - Bengt Herweg
- Cardiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Dany Sayad
- Cardiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Javier Saiz
- Ci2 B, Universitat Politècnica de València, Valencia, Spain
| | - Sami Noujaim
- Molecular Pharmacology and Physiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
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7
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Sun Y, Timofeyev V, Dennis A, Bektik E, Wan X, Laurita KR, Deschênes I, Li RA, Fu JD. A Singular Role of I K1 Promoting the Development of Cardiac Automaticity during Cardiomyocyte Differentiation by I K1 -Induced Activation of Pacemaker Current. Stem Cell Rev Rep 2018. [PMID: 28623610 DOI: 10.1007/s12015-017-9745-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The inward rectifier potassium current (IK1) is generally thought to suppress cardiac automaticity by hyperpolarizing membrane potential (MP). We recently observed that IK1 could promote the spontaneously-firing automaticity induced by upregulation of pacemaker funny current (If) in adult ventricular cardiomyocytes (CMs). However, the intriguing ability of IK1 to activate If and thereby promote automaticity has not been explored. In this study, we combined mathematical and experimental assays and found that only IK1 and If, at a proper-ratio of densities, were sufficient to generate rhythmic MP-oscillations even in unexcitable cells (i.e. HEK293T cells and undifferentiated mouse embryonic stem cells [ESCs]). We termed this effect IK1-induced If activation. Consistent with previous findings, our electrophysiological recordings observed that around 50% of mouse (m) and human (h) ESC-differentiated CMs could spontaneously fire action potentials (APs). We found that spontaneously-firing ESC-CMs displayed more hyperpolarized maximum diastolic potential and more outward IK1 current than quiescent-yet-excitable m/hESC-CMs. Rather than classical depolarization pacing, quiescent mESC-CMs were able to fire APs spontaneously with an electrode-injected small outward-current that hyperpolarizes MP. The automaticity to spontaneously fire APs was also promoted in quiescent hESC-CMs by an IK1-specific agonist zacopride. In addition, we found that the number of spontaneously-firing m/hESC-CMs was significantly decreased when If was acutely upregulated by Ad-CGI-HCN infection. Our study reveals a novel role of IK1 promoting the development of cardiac automaticity in m/hESC-CMs through a mechanism of IK1-induced If activation and demonstrates a synergistic interaction between IK1 and If that regulates cardiac automaticity.
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Affiliation(s)
- Yu Sun
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 Metrohealth Drive, Rammelkamp 650, Cleveland, OH, 44109, USA
| | - Valeriy Timofeyev
- Department of Internal Medicine, University of California, Davis, CA, USA
| | - Adrienne Dennis
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 Metrohealth Drive, Rammelkamp 650, Cleveland, OH, 44109, USA
| | - Emre Bektik
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 Metrohealth Drive, Rammelkamp 650, Cleveland, OH, 44109, USA.,Ph.D. Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Japan
| | - Xiaoping Wan
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 Metrohealth Drive, Rammelkamp 650, Cleveland, OH, 44109, USA
| | - Kenneth R Laurita
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 Metrohealth Drive, Rammelkamp 650, Cleveland, OH, 44109, USA
| | - Isabelle Deschênes
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 Metrohealth Drive, Rammelkamp 650, Cleveland, OH, 44109, USA
| | - Ronald A Li
- Dr. Li Dak-Sum Center for Regenerative Medicine, University of Hong Kong, The Hong Kong Jockey Club Building for Interdisciplinary Research, LB 5-06, 5 Sassoon Road, Pokfulam, Hong Kong. .,Ming-Wai Lau Center for Regenerative Medicine, Karolinska Institutet, Solna, Sweden.
| | - Ji-Dong Fu
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 Metrohealth Drive, Rammelkamp 650, Cleveland, OH, 44109, USA.
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8
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Ji Y, Veldhuis MG, Zandvoort J, Romunde FL, Houtman MJC, Duran K, van Haaften G, Zangerl-Plessl EM, Takanari H, Stary-Weinzinger A, van der Heyden MAG. PA-6 inhibits inward rectifier currents carried by V93I and D172N gain-of-function K IR2.1 channels, but increases channel protein expression. J Biomed Sci 2017; 24:44. [PMID: 28711067 PMCID: PMC5513211 DOI: 10.1186/s12929-017-0352-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 07/11/2017] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND The inward rectifier potassium current IK1 contributes to a stable resting membrane potential and phase 3 repolarization of the cardiac action potential. KCNJ2 gain-of-function mutations V93I and D172N associate with increased IK1, short QT syndrome type 3 and congenital atrial fibrillation. Pentamidine-Analogue 6 (PA-6) is an efficient (IC50 = 14 nM with inside-out patch clamp methodology) and specific IK1 inhibitor that interacts with the cytoplasmic pore region of the KIR2.1 ion channel, encoded by KCNJ2. At 10 μM, PA-6 increases wild-type (WT) KIR2.1 expression in HEK293T cells upon chronic treatment. We hypothesized that PA-6 will interact with and inhibit V93I and D172N KIR2.1 channels, whereas impact on channel expression at the plasma membrane requires higher concentrations. METHODS Molecular modelling was performed with the human KIR2.1 closed state homology model using FlexX. WT and mutant KIR2.1 channels were expressed in HEK293 cells. Patch-clamp single cell electrophysiology measurements were performed in the whole cell and inside-out mode of the patch clamp method. KIR2.1 expression level and localization were determined by western blot analysis and immunofluorescence microscopy, respectively. RESULTS PA-6 docking in the V93I/D172N double mutant homology model of KIR2.1 demonstrated that mutations and drug-binding site are >30 Å apart. PA-6 inhibited WT and V93I outward currents with similar potency (IC50 = 35.5 and 43.6 nM at +50 mV for WT and V93I), whereas D172N currents were less sensitive (IC50 = 128.9 nM at +50 mV) using inside-out patch-clamp electrophysiology. In whole cell mode, 1 μM of PA-6 inhibited outward IK1 at -50 mV by 28 ± 36%, 18 ± 20% and 10 ± 6%, for WT, V93I and D172N channels respectively. Western blot analysis demonstrated that PA-6 (5 μM, 24 h) increased KIR2.1 expression levels of WT (6.3 ± 1.5 fold), and V93I (3.9 ± 0.9) and D172N (4.8 ± 2.0) mutants. Immunofluorescent microscopy demonstrated dose-dependent intracellular KIR2.1 accumulation following chronic PA-6 application (24 h, 1 and 5 μM). CONCLUSIONS 1) KCNJ2 gain-of-function mutations V93I and D172N in the KIR2.1 ion channel do not impair PA-6 mediated inhibition of IK1, 2) PA-6 elevates KIR2.1 protein expression and induces intracellular KIR2.1 accumulation, 3) PA-6 is a strong candidate for further preclinical evaluation in treatment of congenital SQT3 and AF.
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Affiliation(s)
- Yuan Ji
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Marlieke G. Veldhuis
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Jantien Zandvoort
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Fee L. Romunde
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Marien J. C. Houtman
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Karen Duran
- Center for Molecular Medicine, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Gijs van Haaften
- Center for Molecular Medicine, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Hiroki Takanari
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | | | - Marcel A. G. van der Heyden
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
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9
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Scherer D, Schworm B, Seyler C, Xynogalos P, Scholz EP, Thomas D, Katus HA, Zitron E. Inhibition of inwardly rectifying Kir2.x channels by the novel anti-cancer agent gambogic acid depends on both pore block and PIP 2 interference. Naunyn Schmiedebergs Arch Pharmacol 2017; 390:701-710. [PMID: 28365825 DOI: 10.1007/s00210-017-1372-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 03/23/2017] [Indexed: 12/21/2022]
Abstract
The caged xanthone gambogic acid (GA) is a novel anti-cancer agent which exhibits anti-proliferative, anti-inflammatory and cytotoxic effects in many types of cancer tissues. In a recent phase IIa study, GA exhibits a favourable safety profile. However, limited data are available concerning its interaction with cardiac ion channels. Heteromeric assembly of Kir2.x channels underlies the cardiac inwardly rectifying IK1 current which is responsible for the stabilization of the diastolic resting membrane potential. Inhibition of the cardiac IK1 current may lead to ventricular arrhythmia due to delayed afterdepolarizations. Compared to Kv2.1, hERG and Kir1.1, a slow, delayed inhibition of Kir2.1 channels by GA in a mammalian cell line was reported before but no data exist in literature concerning action of GA on homomeric Kir2.2 and Kir2.3 and heteromeric Kir2.x channels. Therefore, the aim of this study was to provide comparative data on the effect of GA on homomeric and heteromeric Kir2.x channels. Homomeric and heteromeric Kir2.x channels were heterologously expressed in Xenopus oocytes, and the two-microelectrode voltage-clamp technique was used to record Kir2.x currents. To investigate the mechanism of the channel inhibition by GA, alanine-mutated Kir2.x channels with modifications in the channels pore region or at phosphatidylinositol 4,5-bisphosphate (PIP2)-binding sites were employed. GA caused a slow inhibition of homomeric and heteromeric Kir2.x channels at low micromolar concentrations (with IC50 Kir2.1/2.2 < Kir2.2 < Kir2.2/2.3 < Kir2.3 < Kir2.1 < Kir2.1/2.3). The effect did not reach saturation within 60 min and was not reversible upon washout for 30 min. The inhibition showed no strong voltage dependence. We provide evidence for a combination of direct channel pore blockade and a PIP2-dependent mechanism as a molecular basis for the observed effect. We conclude that Kir2.x channel inhibition by GA may be relevant in patients with pre-existing cardiac disorders such as chronic heart failure or certain rhythm disorders and recommend a close cardiac monitoring for those patients when treated with GA.
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Affiliation(s)
- Daniel Scherer
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.
| | - Benedikt Schworm
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany
| | - Claudia Seyler
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, Heidelberg, Germany
| | - Panagiotis Xynogalos
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany
| | - Eberhard P Scholz
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, Heidelberg, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, Heidelberg, Germany
| | - Edgar Zitron
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, Heidelberg, Germany
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Wang K, Mateos-Aparicio P, Hönigsperger C, Raghuram V, Wu WW, Ridder MC, Sah P, Maylie J, Storm JF, Adelman JP. IK1 channels do not contribute to the slow afterhyperpolarization in pyramidal neurons. eLife 2016; 5:e11206. [PMID: 26765773 PMCID: PMC4733036 DOI: 10.7554/elife.11206] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 12/01/2015] [Indexed: 11/16/2022] Open
Abstract
In pyramidal neurons such as hippocampal area CA1 and basolateral amygdala, a slow afterhyperpolarization (sAHP) follows a burst of action potentials, which is a powerful regulator of neuronal excitability. The sAHP amplitude increases with aging and may underlie age related memory decline. The sAHP is due to a Ca2+-dependent, voltage-independent K+ conductance, the molecular identity of which has remained elusive until a recent report suggested the Ca2+-activated K+ channel, IK1 (KCNN4) as the sAHP channel in CA1 pyramidal neurons. The signature pharmacology of IK1, blockade by TRAM-34, was reported for the sAHP and underlying current. We have examined the sAHP and find no evidence that TRAM-34 affects either the current underling the sAHP or excitability of CA1 or basolateral amygdala pyramidal neurons. In addition, CA1 pyramidal neurons from IK1 null mice exhibit a characteristic sAHP current. Our results indicate that IK1 channels do not mediate the sAHP in pyramidal neurons. DOI:http://dx.doi.org/10.7554/eLife.11206.001 Neurons carry signals in the form of electrical impulses called action potentials. These nerve impulses result from ions flowing through proteins called ion channels in the neuron’s membrane, and they determine how the neuron communicates with neighboring neurons. The number of action potentials a neuron can produce can vary over a wide range. In the brain, a particular kind of ion channel limits the number of action potentials that many neurons produce via a negative feedback mechanism. That is to say, nerve impulses activate this ion channel and the activated channel then makes the neuron less able to send further nerve impulses for a while.The activity of this ion channel increases with age and it may be responsible for some forms of age-related decline in cognitive abilities. However, the exact identity of the ion channel responsible was unclear. Recent research has suggested the ion channel in question was a protein called IK1. This conclusion was largely based on how this ion channel responded to drugs in the laboratory. Wang, Materos-Aparico et al. sought to verify this conclusion and, in contrast with the previous reports, found that the IK1 ion channel did not respond to these drugs in the same way when it was in neurons in the brains of mice. In further experiments, mice that had been engineered to lack the IK1 ion channel still showed the characteristic negative feedback that regulates the firing of action potentials. Thus, Wang, Materos-Aparico et al. found no evidence to support the previous conclusion, and instead conclude that the exact identity of this important ion channel in the brain has yet to be defined. DOI:http://dx.doi.org/10.7554/eLife.11206.002
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Affiliation(s)
- Kang Wang
- Vollum Institute, Oregon Health and Science University, Portland, United States
| | - Pedro Mateos-Aparicio
- Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Christoph Hönigsperger
- Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Vijeta Raghuram
- Vollum Institute, Oregon Health and Science University, Portland, United States
| | - Wendy W Wu
- Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, United States
| | - Margreet C Ridder
- Queensland Brain Institute, The University of Queensland, Brisbane, Australia
| | - Pankaj Sah
- Queensland Brain Institute, The University of Queensland, Brisbane, Australia
| | - Jim Maylie
- Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, United States
| | - Johan F Storm
- Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - John P Adelman
- Vollum Institute, Oregon Health and Science University, Portland, United States
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Lin MT, Jian MY, Taylor MS, Cioffi DL, Yap FC, Liedtke W, Townsley MI. Functional coupling of TRPV4, IK, and SK channels contributes to Ca(2+)-dependent endothelial injury in rodent lung. Pulm Circ 2015; 5:279-90. [PMID: 26064452 DOI: 10.1086/680166] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 09/15/2014] [Indexed: 02/05/2023] Open
Abstract
Our previous work has shown that the increased lung endothelial permeability response to 14,15-epoxyeicosatrienoic acid (14,15-EET) in rat lung requires Ca(2+) entry via vanilloid type-4 transient receptor potential (TRPV4) channels. Recent studies suggest that activation of TRPV4 channels in systemic vascular endothelium prolongs agonist-induced hyperpolarization and amplifies Ca(2+) entry by activating Ca(2+)-activated K(+) (KCa) channels, resulting in vessel relaxation. Activation of endothelial KCa channels thus has potential to increase the electrochemical driving force for Ca(2+) influx via TRPV4 channels and to amplify permeability responses to TRPV4 activation in lung. To examine this hypothesis, we used Western blot analysis, electrophysiological recordings, and isolated-lung permeability measurements to document expression of TRPV4 and KCa channels and the potential for functional coupling. The results show that rat pulmonary microvascular endothelial cells express TRPV4 and 3 KCa channels of different conductances: large (BK), intermediate (IK), and small (SK3). However, TRPV4 channel activity modulates the IK and SK3, but not the BK, channel current density. Furthermore, the TRPV4-mediated permeability response to 14,15-EET in mouse lung is significantly attenuated by pharmacologic blockade of IK and SK3, but not BK, channels. Collectively, this functional coupling suggests that endothelial TRPV4 channels in rodent lung likely form signaling microdomains with IK and SK3 channels and that the integrated response dictates the extent of lung endothelial injury caused by 14,15-EET.
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Affiliation(s)
- Mike T Lin
- Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama, USA ; These authors contributed equally to this work
| | - Ming-Yuan Jian
- Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama, USA ; Center for Lung Biology, University of South Alabama, Mobile, Alabama, USA ; Present address: Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, Alabama, USA. ; These authors contributed equally to this work
| | - Mark S Taylor
- Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama, USA
| | - Donna L Cioffi
- Center for Lung Biology, University of South Alabama, Mobile, Alabama, USA ; Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Fui C Yap
- Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama, USA
| | - Wolfgang Liedtke
- Departments of Medicine, Neurology and Neurobiology, Duke University, Durham, North Carolina, USA
| | - Mary I Townsley
- Department of Physiology and Cell Biology, University of South Alabama, Mobile, Alabama, USA ; Center for Lung Biology, University of South Alabama, Mobile, Alabama, USA ; Department of Medicine, University of South Alabama, Mobile, Alabama, USA
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Gómez R, Caballero R, Barana A, Amorós I, De Palm SH, Matamoros M, Núñez M, Pérez-Hernández M, Iriepa I, Tamargo J, Delpón E. Structural basis of drugs that increase cardiac inward rectifier Kir2.1 currents. Cardiovasc Res 2014; 104:337-46. [PMID: 25205296 DOI: 10.1093/cvr/cvu203] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AIMS We hypothesize that some drugs, besides flecainide, increase the inward rectifier current (IK1) generated by Kir2.1 homotetramers (IKir2.1) and thus, exhibit pro- and/or antiarrhythmic effects particularly at the ventricular level. To test this hypothesis, we analysed the effects of propafenone, atenolol, dronedarone, and timolol on Kir2.x channels. METHODS AND RESULTS Currents were recorded with the patch-clamp technique using whole-cell, inside-out, and cell-attached configurations. Propafenone (0.1 nM-1 µM) did not modify either IK1 recorded in human right atrial myocytes or the current generated by homo- or heterotetramers of Kir2.2 and 2.3 channels recorded in transiently transfected Chinese hamster ovary cells. On the other hand, propafenone increased IKir2.1 (EC50 = 12.0 ± 3.0 nM) as a consequence of its interaction with Cys311, an effect which decreased inward rectification of the current. Propafenone significantly increased mean open time and opening frequency at all the voltages tested, resulting in a significant increase of the mean open probability of the channel. Timolol, which interacted with Cys311, was also able to increase IKir2.1. On the contrary, neither atenolol nor dronedarone modified IKir2.1. Molecular modelling of the Kir2.1-drugs interaction allowed identification of the pharmacophore of drugs that increase IKir2.1. CONCLUSIONS Kir2.1 channels exhibit a binding site determined by Cys311 that is responsible for drug-induced IKir2.1 increase. Drug binding decreases channel affinity for polyamines and current rectification, and can be a mechanism of drug-induced pro- and antiarrhythmic effects not considered until now.
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Affiliation(s)
- Ricardo Gómez
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain
| | - Ricardo Caballero
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain
| | - Adriana Barana
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Hospital Clínico San Carlos, School of Medicine, Universidad Complutense, Madrid, Spain
| | - Irene Amorós
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain
| | - Sue-Haida De Palm
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain
| | - Marcos Matamoros
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain
| | - Mercedes Núñez
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain
| | - Marta Pérez-Hernández
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Hospital Clínico San Carlos, School of Medicine, Universidad Complutense, Madrid, Spain
| | - Isabel Iriepa
- Department of Organic Chemistry, School of Pharmacy, Universidad de Alcalá, Alcalá de Henares, Spain
| | - Juan Tamargo
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Hospital Clínico San Carlos, School of Medicine, Universidad Complutense, Madrid, Spain
| | - Eva Delpón
- Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain
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