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AlRawashdeh S, Chandrasekaran S, Barakat KH. Structural analysis of hERG channel blockers and the implications for drug design. J Mol Graph Model 2023; 120:108405. [PMID: 36680816 DOI: 10.1016/j.jmgm.2023.108405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 12/26/2022] [Accepted: 01/09/2023] [Indexed: 01/13/2023]
Abstract
The repolarizing current (Ikr) produced by the hERG potassium channel forms a major component of the cardiac action potential and blocking this current by small molecule drugs can lead to life-threatening cardiotoxicity. Understanding the mechanisms of drug-mediated hERG inhibition is essential to develop a second generation of safe drugs, with minimal cardiotoxic effects. Although various computational tools and drug design guidelines have been developed to avoid binding of drugs to the hERG pore domain, there are many other aspects that are still open for investigation. This includes the use computational modelling to study the implications of hERG mutations on hERG structure and trafficking, the interactions of hERG with hERG chaperone proteins and with membrane-soluble molecules, the mechanisms of drugs that inhibit hERG trafficking and drugs that rescue hERG mutations. The plethora of available experimental data regarding all these aspects can guide the construction of much needed robust computational structural models to study these mechanisms for the rational design of safe drugs.
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Affiliation(s)
- Sara AlRawashdeh
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB, Canada
| | | | - Khaled H Barakat
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB, Canada.
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2
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Abdelrady AM, Zaitone SA, Farag NE, Fawzy MS, Moustafa YM. Cardiotoxic effect of levofloxacin and ciprofloxacin in rats with/without acute myocardial infarction: Impact on cardiac rhythm and cardiac expression of Kv4.3, Kv1.2 and Nav1.5 channels. Biomed Pharmacother 2017; 92:196-206. [PMID: 28544933 DOI: 10.1016/j.biopha.2017.05.049] [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: 01/07/2017] [Revised: 05/06/2017] [Accepted: 05/09/2017] [Indexed: 10/19/2022] Open
Abstract
Prolongation of QT interval is possible with fluoroquinolones, yet the underlying contributing factors have not been elucidated. Two widely used fluoroquinolone drugs were at the focus of this study in rats with/without acute myocardial dysfunction (AMI) induced by isoproterenol. The effects of levofloxacin and ciprofloxacin on the cardiac mRNA expression of rat Kv4.3, Kv1.2 and Nav1.5 mRNAs were determined. Administration of the two antibiotics produced dose-dependent changes in ECG parameters that were more prominent in rats with AMI than healthy rats; this was accompanied by elevations in serum lactate dehydrogenase and creatine kinase-MB. Histopathological examination indicated some loss of striations, edema and fibrotic changes in rats with AMI; however the two antibiotics did not further exacerbate the cardiac histopathology. mRNA expression of the ion channels was altered in rats with AMI and healthy rats. In conclusion, long-term administration of levofloxacin and ciprofloxacin produced deleterious effects on the ECG pattern of rats with/without AMI. The effect was generally baseline-dependent and therefore, rats with AMI showed greater ECG disturbances and increases in cardiac enzymes. Taken together, these data make it advisable to monitor patients with a history of acute AMI requiring treatment with these antibiotics until data from human studies are available.
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Affiliation(s)
| | - Sawsan A Zaitone
- Deparment of Pharmacology & Toxicology, Faculty of Pharmacy, Suez Canal University, 41522, Ismailia, Egypt; Deparment of Pharmacology & Toxicology, Faculty of Pharmacy, University of Tabuk, Saudi Arabia.
| | - Noha E Farag
- Deparment of Physiology, Faculty of Medicine, Suez Canal University, Ismailia, Egypt
| | - Manal S Fawzy
- Deparment of Medical Biochemistry, Faculty of Medicine, Suez Canal University, Ismailia, Egypt
| | - Yasser M Moustafa
- Deparment of Pharmacology & Toxicology, Faculty of Pharmacy, Suez Canal University, 41522, Ismailia, Egypt
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Martínez-Mármol R, Pérez-Verdaguer M, Roig SR, Vallejo-Gracia A, Gotsi P, Serrano-Albarrás A, Bahamonde MI, Ferrer-Montiel A, Fernández-Ballester G, Comes N, Felipe A. A non-canonical di-acidic signal at the C-terminus of Kv1.3 determines anterograde trafficking and surface expression. J Cell Sci 2013; 126:5681-91. [PMID: 24144698 DOI: 10.1242/jcs.134825] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Impairment of Kv1.3 expression at the cell membrane in leukocytes and sensory neuron contributes to the pathophysiology of autoimmune diseases and sensory syndromes. Molecular mechanisms underlying Kv1.3 channel trafficking to the plasma membrane remain elusive. We report a novel non-canonical di-acidic signal (E483/484) at the C-terminus of Kv1.3 essential for anterograde transport and surface expression. Notably, homologous motifs are conserved in neuronal Kv1 and Shaker channels. Biochemical analysis revealed interactions with the Sec24 subunit of the coat protein complex II. Disruption of this complex retains the channel at the endoplasmic reticulum. A molecular model of the Kv1.3-Sec24a complex suggests salt-bridges between the di-acidic E483/484 motif in Kv1.3 and the di-basic R750/752 sequence in Sec24. These findings identify a previously unrecognized motif of Kv channels essential for their expression on the cell surface. Our results contribute to our understanding of how Kv1 channels target to the cell membrane, and provide new therapeutic strategies for the treatment of pathological conditions.
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Affiliation(s)
- Ramón Martínez-Mármol
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Av. Diagonal 643, E-08028 Barcelona, Spain
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Özgen N, Lu Z, Boink GJJ, Lau DH, Shlapakova IN, Bobkov Y, Danilo P, Cohen IS, Rosen MR. Microtubules and angiotensin II receptors contribute to modulation of repolarization induced by ventricular pacing. Heart Rhythm 2012; 9:1865-72. [PMID: 22820054 DOI: 10.1016/j.hrthm.2012.07.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Indexed: 01/09/2023]
Abstract
BACKGROUND Left ventricular pacing (LVP) in canine heart alters ventricular activation, leading to reduced transient outward potassium current (I(to)), loss of the epicardial action potential notch, and T-wave vector displacement. These repolarization changes, referred to as cardiac memory, are initiated by locally increased angiotensin II (AngII) levels. In HEK293 cells in which Kv4.3 and KChIP2, the channel subunits contributing to I(to), are overexpressed with the AngII receptor 1 (AT1R), AngII induces a decrease in I(to) as the result of internalization of a Kv4.3/KChIP2/AT1R macromolecular complex. OBJECTIVE To test the hypothesis that in canine heart in situ, 2h LVP-induced decreases in membrane KChIP2, AT1R, and I(to) are prevented by blocking subunit trafficking. METHODS We used standard electrophysiological, biophysical, and biochemical methods to study 4 groups of dogs: (1) Sham, (2) 2h LVP, (3) LVP + colchicine (microtubule-disrupting agent), and (4) LVP + losartan (AT1R blocker). RESULTS The T-wave vector displacement was significantly greater in LVP than in Sham and was inhibited by colchicine or losartan. Epicardial biopsies showed significant decreases in KChIP2 and AT1R proteins in the membrane fraction after LVP but not after sham treatment, and these decreases were prevented by colchicine or losartan. Colchicine but not losartan significantly reduced microtubular polymerization. In isolated ventricular myocytes, AngII-induced I(to) reduction and loss of action potential notch were blocked by colchicine. CONCLUSIONS LVP-induced reduction of KChIP2 in plasma light membranes depends on an AngII-mediated pathway and intact microtubular status. Loss of I(to) and the action potential notch appear to derive from AngII-initiated trafficking of channel subunits.
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Affiliation(s)
- Nazira Özgen
- Department of Pharmacology, Columbia University, New York, New York 10032, USA
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Song MY, Hong C, Bae SH, So I, Park KS. Dynamic modulation of the kv2.1 channel by SRC-dependent tyrosine phosphorylation. J Proteome Res 2012; 11:1018-26. [PMID: 22106938 PMCID: PMC3272096 DOI: 10.1021/pr200770v] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The voltage-gated K(+) channel Kv2.1 is expressed as a highly phosphorylated protein in most central neurons, where it plays a key role in regulating neuronal membrane excitability. Previous studies have shown that Kv2.1 channel activity is upregulated by Src-mediated phosphorylation through an unknown mechanism. However, a systematic analysis of the molecular mechanism of Kv2.1 channel phosphorylation by Src is lacking. Here, we show that tyrosine phosphorylation by Src plays a fundamental role in regulating Kv2.1-mediated K(+) current enhancement. We found that the level of expression of the Kv2.1 protein is increased by Src kinase. Using mass spectrometric proteomic techniques, we identified two novel phosphotyrosine sites, Y686 and Y810, in the cytoplasmic domains of Kv2.1. We found that Src-dependent phosphorylation at these sites affects Kv2.1 through distinct regulatory mechanisms. Whereas phosphorylation at Y686 regulates Kv2.1 activity similarly to the known site Y124, phosphorylation at Y810 plays a significant role in regulating the intracellular trafficking of Kv2.1 channels. Our results show that these two novel tyrosine phosphorylation sites of Kv2.1 are crucial to regulating diverse aspects of Kv2.1 channel function and provide novel insights into molecular mechanisms for the regulation of Src-dependent modulation of Kv2.1 channels.
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Affiliation(s)
- Min-Young Song
- Department of Physiology, Kyung Hee University School of Medicine, Seoul 130-701, South Korea
- Biomedical Science Institute, Kyung Hee University School of Medicine, Seoul 130-701, South Korea
| | - Chansik Hong
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, South Korea
| | - Seong Han Bae
- Department of Physiology, Kyung Hee University School of Medicine, Seoul 130-701, South Korea
- Biomedical Science Institute, Kyung Hee University School of Medicine, Seoul 130-701, South Korea
| | - Insuk So
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, South Korea
| | - Kang-Sik Park
- Department of Physiology, Kyung Hee University School of Medicine, Seoul 130-701, South Korea
- Biomedical Science Institute, Kyung Hee University School of Medicine, Seoul 130-701, South Korea
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Roura-Ferrer M, Solé L, Oliveras A, Dahan R, Bielanska J, Villarroel A, Comes N, Felipe A. Impact of KCNE subunits on KCNQ1 (Kv7.1) channel membrane surface targeting. J Cell Physiol 2010; 225:692-700. [PMID: 20533308 DOI: 10.1002/jcp.22265] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The KCNQ1 (Kv7.1) channel plays an important role in cardiovascular physiology. Cardiomyocytes co-express KCNQ1 with KCNE1-5 proteins. KCNQ1 may co-associate with multiple KCNE regulatory subunits to generate different biophysically and pharmacologically distinct channels. Increasing evidence indicates that the location and targeting of channels are important determinants of their function. In this context, the presence of K(+) channels in sphingolipid-cholesterol-enriched membrane microdomains (lipid rafts) is under investigation. Lipid rafts are important for cardiovascular functioning. We aimed to determine whether KCNE subunits modify the localization and targeting of KCNQ1 channels in lipid rafts microdomains. HEK-293 cells were transiently transfected with KCNQ1 and KCNE1-5, and their traffic and presence in lipid rafts were analyzed. Only KCNQ1 and KCNE3, when expressed alone, co-localized in raft fractions. In addition, while KCNE2 and KCNE5 notably stained the cell surface, KCNQ1 and the rest of the KCNEs showed strong intracellular retention. KCNQ1 targets multiple membrane surface microdomains upon association with KCNE peptides. Thus, while KCNQ1/KCNE1 and KCNQ1/KCNE2 channels target lipid rafts, KCNQ1 associated with KCNE3-5 did not. Channel membrane dynamics, analyzed by fluorescence recovery after photobleaching (FRAP) experiments, further supported these results. In conclusion, the trafficking and targeting pattern of KCNQ1 can be influenced by its association with KCNEs. Since KCNQ1 is crucial for cardiovascular physiology, the temporal and spatial regulations that different KCNE subunits may confer to the channels could have a dramatic impact on membrane electrical activity and putative endocrine regulation.
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Affiliation(s)
- Meritxell Roura-Ferrer
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
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Buxton ILO, Singer CA, Tichenor JN. Expression of stretch-activated two-pore potassium channels in human myometrium in pregnancy and labor. PLoS One 2010; 5:e12372. [PMID: 20811500 PMCID: PMC2928262 DOI: 10.1371/journal.pone.0012372] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 07/30/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND We tested the hypothesis that the stretch-activated, four-transmembrane domain, two pore potassium channels (K2P), TREK-1 and TRAAK are gestationally-regulated in human myometrium and contribute to uterine relaxation during pregnancy until labor. METHODOLOGY We determined the gene and protein expression of K2P channels in non-pregnant, pregnant term and preterm laboring myometrium. We employed both molecular biological and functional studies of K2P channels in myometrial samples taken from women undergoing cesarean delivery of a fetus. PRINCIPAL FINDINGS TREK-1, but not TREK-2, channels are expressed in human myometrium and significantly up-regulated during pregnancy. Down-regulation of TREK-1 message was seen by Q-PCR in laboring tissues consistent with a role for TREK-1 in maintaining uterine quiescence prior to labor. The TRAAK channel was unregulated in the same women. Blockade of stretch-activated channels with a channel non-specific tarantula toxin (GsMTx-4) or the more specific TREK-1 antagonist L-methionine ethyl ester altered contractile frequency in a dose-dependent manner in pregnant myometrium. Arachidonic acid treatment lowered contractile tension an effect blocked by fluphenazine. Functional studies are consistent with a role for TREK-1 in uterine quiescence. CONCLUSIONS We provide evidence supporting a role for TREK-1 in contributing to uterine quiescence during gestation and hypothesize that dysregulation of this mechanism may underlie certain cases of spontaneous pre-term birth.
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Affiliation(s)
- Iain L O Buxton
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Nevada, United States of America.
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Schumacher SM, Martens JR. Ion channel trafficking: a new therapeutic horizon for atrial fibrillation. Heart Rhythm 2010; 7:1309-15. [PMID: 20156596 DOI: 10.1016/j.hrthm.2010.02.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 02/08/2010] [Indexed: 02/02/2023]
Abstract
Atrial fibrillation (AF) is a common cardiac arrhythmia with potentially life-threatening complications. Drug therapies for treatment of AF that seek long-term maintenance of normal sinus rhythm remain elusive due in large part to proarrhythmic ventricular actions. Kv1.5, which underlies the atrial specific I(Kur) current, is a major focus of research efforts seeking new therapeutic strategies and targets. Recent work has shown a novel effect of antiarrhythmic drugs where compounds that block Kv1.5 channel current also can alter ion channel trafficking. This work further suggests that the pleiotropic effects of antiarrhythmic drugs may be separable. Although this finding highlights the therapeutic potential for selective manipulation of ion channel surface density, it also reveals an uncertainty regarding the specificity of modulating trafficking pathways without risk of off-target effects. Future studies may show that specific alteration of Kv1.5 trafficking can overcome the proarrhythmic limitations of current pharmacotherapy and provide an effective method for long-term cardioversion in AF.
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Affiliation(s)
- Sarah M Schumacher
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
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Alpha-actinin2 cytoskeletal protein is required for the functional membrane localization of a Ca2+-activated K+ channel (SK2 channel). Proc Natl Acad Sci U S A 2009; 106:18402-7. [PMID: 19815520 DOI: 10.1073/pnas.0908207106] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The importance of proper ion channel trafficking is underpinned by a number of channel-linked genetic diseases whose defect is associated with failure to reach the cell surface. Conceptually, it is reasonable to suggest that the function of ion channels depends critically on the precise subcellular localization and the number of channel proteins on the cell surface membrane, which is determined jointly by the secretory and endocytic pathways. Yet the precise mechanisms of the entire ion channel trafficking pathway remain unknown. Here, we directly demonstrate that proper membrane localization of a small-conductance Ca(2+)-activated K(+) channel (SK2 or K(Ca)2.2) is dependent on its interacting protein, alpha-actinin2, a major F-actin crosslinking protein. SK2 channel localization on the cell-surface membrane is dynamically regulated, and one of the critical steps includes the process of cytoskeletal anchoring of SK2 channel by its interacting protein, alpha-actinin2, as well as endocytic recycling via early endosome back to the cell membrane. Consequently, alteration of these components of SK2 channel recycling results in profound changes in channel surface expression. The importance of our findings may transcend the area of K(+) channels, given that similar cytoskeletal interaction and anchoring may be critical for the membrane localization of other ion channels in neurons and other excitable cells.
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