1
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Fedida D, Sastre D, Dou Y, Westhoff M, Eldstrom J. Evaluating sequential and allosteric activation models in IKs channels with mutated voltage sensors. J Gen Physiol 2024; 156:e202313465. [PMID: 38294435 PMCID: PMC10829594 DOI: 10.1085/jgp.202313465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 11/30/2023] [Accepted: 01/03/2024] [Indexed: 02/01/2024] Open
Abstract
The ion-conducting IKs channel complex, important in cardiac repolarization and arrhythmias, comprises tetramers of KCNQ1 α-subunits along with 1-4 KCNE1 accessory subunits and calmodulin regulatory molecules. The E160R mutation in individual KCNQ1 subunits was used to prevent activation of voltage sensors and allow direct determination of transition rate data from complexes opening with a fixed number of 1, 2, or 4 activatable voltage sensors. Markov models were used to test the suitability of sequential versus allosteric models of IKs activation by comparing simulations with experimental steady-state and transient activation kinetics, voltage-sensor fluorescence from channels with two or four activatable domains, and limiting slope currents at negative potentials. Sequential Hodgkin-Huxley-type models approximately describe IKs currents but cannot explain an activation delay in channels with only one activatable subunit or the hyperpolarizing shift in the conductance-voltage relationship with more activatable voltage sensors. Incorporating two voltage sensor activation steps in sequential models and a concerted step in opening via rates derived from fluorescence measurements improves models but does not resolve fundamental differences with experimental data. Limiting slope current data that show the opening of channels at negative potentials and very low open probability are better simulated using allosteric models of activation with one transition per voltage sensor, which implies that movement of all four sensors is not required for IKs conductance. Tiered allosteric models with two activating transitions per voltage sensor can fully account for IKs current and fluorescence activation kinetics in constructs with different numbers of activatable voltage sensors.
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Affiliation(s)
- David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Daniel Sastre
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
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2
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Chan M, Sahakyan H, Eldstrom J, Sastre D, Wang Y, Dou Y, Pourrier M, Vardanyan V, Fedida D. A generic binding pocket for small molecule IKs activators at the extracellular inter-subunit interface of KCNQ1 and KCNE1 channel complexes. eLife 2023; 12:RP87038. [PMID: 37707495 PMCID: PMC10501768 DOI: 10.7554/elife.87038] [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] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2023] Open
Abstract
The cardiac IKs ion channel comprises KCNQ1, calmodulin, and KCNE1 in a dodecameric complex which provides a repolarizing current reserve at higher heart rates and protects from arrhythmia syndromes that cause fainting and sudden death. Pharmacological activators of IKs are therefore of interest both scientifically and therapeutically for treatment of IKs loss-of-function disorders. One group of chemical activators are only active in the presence of the accessory KCNE1 subunit and here we investigate this phenomenon using molecular modeling techniques and mutagenesis scanning in mammalian cells. A generalized activator binding pocket is formed extracellularly by KCNE1, the domain-swapped S1 helices of one KCNQ1 subunit and the pore/turret region made up of two other KCNQ1 subunits. A few residues, including K41, A44 and Y46 in KCNE1, W323 in the KCNQ1 pore, and Y148 in the KCNQ1 S1 domain, appear critical for the binding of structurally diverse molecules, but in addition, molecular modeling studies suggest that induced fit by structurally different molecules underlies the generalized nature of the binding pocket. Activation of IKs is enhanced by stabilization of the KCNQ1-S1/KCNE1/pore complex, which ultimately slows deactivation of the current, and promotes outward current summation at higher pulse rates. Our results provide a mechanistic explanation of enhanced IKs currents by these activator compounds and provide a map for future design of more potent therapeutically useful molecules.
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Affiliation(s)
- Magnus Chan
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Harutyun Sahakyan
- Laboratory of Computational Modeling of Biological Processes, Institute of Molecular BiologyYerevanArmenia
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Daniel Sastre
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Yundi Wang
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Marc Pourrier
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Vitya Vardanyan
- Molecular Neuroscience Group, Institute of Molecular BiologyYerevanArmenia
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
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3
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Abrahamyan A, Eldstrom J, Sahakyan H, Karagulyan N, Mkrtchyan L, Karapetyan T, Sargsyan E, Kneussel M, Nazaryan K, Schwarz JR, Fedida D, Vardanyan V. Mechanism of external K+ sensitivity of KCNQ1 channels. J Gen Physiol 2023; 155:213880. [PMID: 36809486 PMCID: PMC9960071 DOI: 10.1085/jgp.202213205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 12/20/2022] [Accepted: 01/31/2023] [Indexed: 02/23/2023] Open
Abstract
KCNQ1 voltage-gated K+ channels are involved in a wide variety of fundamental physiological processes and exhibit the unique feature of being markedly inhibited by external K+. Despite the potential role of this regulatory mechanism in distinct physiological and pathological processes, its exact underpinnings are not well understood. In this study, using extensive mutagenesis, molecular dynamics simulations, and single-channel recordings, we delineate the molecular mechanism of KCNQ1 modulation by external K+. First, we demonstrate the involvement of the selectivity filter in the external K+ sensitivity of the channel. Then, we show that external K+ binds to the vacant outermost ion coordination site of the selectivity filter inducing a diminution in the unitary conductance of the channel. The larger reduction in the unitary conductance compared to whole-cell currents suggests an additional modulatory effect of external K+ on the channel. Further, we show that the external K+ sensitivity of the heteromeric KCNQ1/KCNE complexes depends on the type of associated KCNE subunits.
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Affiliation(s)
- Astghik Abrahamyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia , Vancouver, BC, Canada
| | - Harutyun Sahakyan
- Laboratory of Computational Modeling of Biological Processes, Institute of Molecular Biology of National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Nare Karagulyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Liana Mkrtchyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Tatev Karapetyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Ernest Sargsyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Matthias Kneussel
- Institute for Molecular Neurogenetics, Center for Molecular Neurobiology Hamburg , Hamburg, Germany
| | - Karen Nazaryan
- Laboratory of Computational Modeling of Biological Processes, Institute of Molecular Biology of National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Jürgen R Schwarz
- Institute for Molecular Neurogenetics, Center for Molecular Neurobiology Hamburg , Hamburg, Germany
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia , Vancouver, BC, Canada
| | - Vitya Vardanyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
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4
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Kyriakis E, Eldstrom J, Willegems K, Ataei F, Sahakyan H, Dou Y, Russo S, Van Petegem F, Fedida D. Structural insights for the modulation of KCNQ1 channel by ML277. Biophys J 2023; 122:21a. [PMID: 36783072 DOI: 10.1016/j.bpj.2022.11.341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Efthymios Kyriakis
- Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Jodene Eldstrom
- Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Katrien Willegems
- Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Fariba Ataei
- Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Harutyun Sahakyan
- National Center for Biotechnology Information, National Library of Medicine, National Institutes for Health, Bethesda, MD, USA
| | - Ying Dou
- Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Sophia Russo
- Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Filip Van Petegem
- Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - David Fedida
- Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, BC, Canada
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5
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Chan M, Sahakyan H, Wang Y, Eldstrom JR, Pourrier M, Vardanyan VA, Fedida D. A mutational and modeling study of a binding pocket for I Ks activators between KCNQ1 and KCNE1. Biophys J 2023; 122:386a-387a. [PMID: 36783958 DOI: 10.1016/j.bpj.2022.11.2116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Magnus Chan
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Harutyun Sahakyan
- Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia, Yerevan, Armenia
| | - Yundi Wang
- Graduate Program in Neuroscience, University of British Columbia, Vancouver, BC, Canada
| | - Jodene R Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Marc Pourrier
- IonsGate Preclinical Services, Vancouver, BC, Canada
| | - Vitya A Vardanyan
- Institute for Neural Signal Transduction, Center for Molecular Neurobiology Hamburg, Hamburg, Germany
| | - David Fedida
- Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
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6
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Willegems K, Eldstrom J, Kyriakis E, Ataei F, Sahakyan H, Dou Y, Russo S, Van Petegem F, Fedida D. Structural and electrophysiological basis for the modulation of KCNQ1 channel currents by ML277. Nat Commun 2022; 13:3760. [PMID: 35768468 PMCID: PMC9243137 DOI: 10.1038/s41467-022-31526-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 06/17/2022] [Indexed: 01/10/2023] Open
Abstract
The KCNQ1 ion channel plays critical physiological roles in electrical excitability and K+ recycling in organs including the heart, brain, and gut. Loss of function is relatively common and can cause sudden arrhythmic death, sudden infant death, epilepsy and deafness. Here, we report cryogenic electron microscopic (cryo-EM) structures of Xenopus KCNQ1 bound to Ca2+/Calmodulin, with and without the KCNQ1 channel activator, ML277. A single binding site for ML277 was identified, localized to a pocket lined by the S4-S5 linker, S5 and S6 helices of two separate subunits. Several pocket residues are not conserved in other KCNQ isoforms, explaining specificity. MD simulations and point mutations support this binding location for ML277 in open and closed channels and reveal that prevention of inactivation is an important component of the activator effect. Our work provides direction for therapeutic intervention targeting KCNQ1 loss of function pathologies including long QT interval syndrome and seizures. KCNQ1 channels are active in heart, brain and gut. Functional loss causes epilepsy and sudden arrhythmic death. Here, authors describe a key activator drug binding site, explaining isoform and drug selectivity, and point the way for new drug design.
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Affiliation(s)
- Katrien Willegems
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada.,Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Efthimios Kyriakis
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Fariba Ataei
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Harutyun Sahakyan
- National Center for Biotechnology Information, National Library of Medicine, National Institutes for Health, Bethesda, MD, USA
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Sophia Russo
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada.
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7
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Chen IS, Eldstrom J, Fedida D, Kubo Y. A novel ion conducting route besides the central pore in an inherited mutant of G-protein-gated inwardly rectifying K + channel. J Physiol 2021; 600:603-622. [PMID: 34881429 DOI: 10.1113/jp282430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [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: 09/28/2021] [Accepted: 11/25/2021] [Indexed: 01/21/2023] Open
Abstract
G-protein-gated inwardly rectifying K+ (GIRK; Kir3.x) channels play important physiological roles in various organs. Some of the disease-associated mutations of GIRK channels are known to induce loss of K+ selectivity but their structural changes remain unclear. In this study, we investigated the mechanisms underlying the abnormal ion selectivity of inherited GIRK mutants. By the two-electrode voltage-clamp analysis of GIRK mutants heterologously expressed in Xenopus oocytes, we observed that Kir3.2 G156S permeates Li+ better than Rb+ , while T154del or L173R of Kir3.2 and T158A of Kir3.4 permeate Rb+ better than Li+ , suggesting a unique conformational change in the G156S mutant. Applications of blockers of the selectivity filter (SF) pathway, Ba2+ or Tertiapin-Q (TPN-Q), remarkably increased the Li+ -selectivity of Kir3.2 G156S but did not alter those of the other mutants. In single-channel recordings of Kir3.2 G156S expressed in mouse fibroblasts, two types of events were observed, one attributable to a TPN-Q-sensitive K+ current and the second a TPN-Q-resistant Li+ current. The results show that a novel Li+ -permeable and blocker-resistant pathway exists in G156S in addition to the SF pathway. Mutations in the pore helix, S148F and T151A also induced high Li+ permeation. Our results demonstrate that the mechanism underlying the loss of K+ selectivity of Kir3.2 G156S involves formation of a novel ion permeation pathway besides the SF pathway, which allows permeation of various species of cations. KEY POINTS: G-protein-gated inwardly rectifying K+ (GIRK; Kir3.x) channels play important roles in controlling excitation of cells in various organs, such as the brain and the heart. Some of the disease-associated mutations of GIRK channels are known to induce loss of K+ selectivity but their structural changes remain unclear. In this study, we investigated the mechanisms underlying the abnormal ion selectivity of inherited mutants of Kir3.2 and Kir3.4. Here we show that a novel Na+ , Li+ -permeable and blocker-resistant pathway exists in an inherited mutant, Kir3.2 G156S, in addition to the conventional ion conducting pathway formed by the selectivity filter (SF). Our results demonstrate that the mechanism underlying the loss of K+ selectivity of Kir3.2 G156S involves formation of a novel ion permeation pathway besides the SF pathway, which allows permeation of various species of cations.
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Affiliation(s)
- I-Shan Chen
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Japan.,Department of Pharmacology, School of Medicine, Wakayama Medical University, Wakayama, Japan
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Japan
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8
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Eldstrom J, McAfee DA, Dou Y, Wang Y, Fedida D. ML277 regulates KCNQ1 single-channel amplitudes and kinetics, modified by voltage sensor state. J Gen Physiol 2021; 153:212696. [PMID: 34636894 PMCID: PMC8515649 DOI: 10.1085/jgp.202112969] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 07/16/2021] [Accepted: 09/15/2021] [Indexed: 11/25/2022] Open
Abstract
KCNQ1 is a pore-forming K+ channel subunit critically important to cardiac repolarization at high heart rates. (2R)-N-[4-(4-methoxyphenyl)-2-thiazolyl]-1-[(4-methylphenyl)sulfonyl]-2 piperidinecarboxamide, or ML277, is an activator of this channel that rescues function of pathophysiologically important mutant channel complexes in human induced pluripotent stem cell–derived cardiomyocytes, and that therefore may have therapeutic potential. Here we extend our understanding of ML277 actions through cell-attached single-channel recordings of wild-type and mutant KCNQ1 channels with voltage sensor domains fixed in resting, intermediate, and activated states. ML277 has profound effects on KCNQ1 single-channel kinetics, eliminating the flickering nature of the openings, converting them to discrete opening bursts, and increasing their amplitudes approximately threefold. KCNQ1 single-channel behavior after ML277 treatment most resembles IO state-locked channels (E160R/R231E) rather than AO state channels (E160R/R237E), suggesting that at least during ML277 treatment, KCNQ1 does not frequently visit the AO state. Introduction of KCNE1 subunits reduces the effectiveness of ML277, but some enhancement of single-channel openings is still observed.
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Affiliation(s)
- Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Donald A McAfee
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Yundi Wang
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
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9
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Abstract
Kv7 channels (Kv7.1-7.5) are voltage-gated K+ channels that can be modulated by five β-subunits (KCNE1-5). Kv7.1-KCNE1 channels produce the slow-delayed rectifying K+ current, IKs, which is important during the repolarization phase of the cardiac action potential. Kv7.2-7.5 are predominantly neuronally expressed and constitute the muscarinic M-current and control the resting membrane potential in neurons. Kv7.1 produces drastically different currents as a result of modulation by KCNE subunits. This flexibility allows the Kv7.1 channel to have many roles depending on location and assembly partners. The pharmacological sensitivity of Kv7.1 channels differs from that of Kv7.2-7.5 and is largely dependent upon the number of β-subunits present in the channel complex. As a result, the development of pharmaceuticals targeting Kv7.1 is problematic. This review discusses the roles and the mechanisms by which different signaling pathways affect Kv7.1 and KCNE channels and could potentially provide different ways of targeting the channel.
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Affiliation(s)
- Emely Thompson
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada;
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada;
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada;
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10
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Abstract
The IKs channel complex is formed by the co-assembly of Kv7.1 (KCNQ1), a voltage-gated potassium channel, with its β-subunit, KCNE1 and the association of numerous accessory regulatory molecules such as PIP2, calmodulin, and yotiao. As a result, the IKs potassium current shows kinetic and regulatory flexibility, which not only allows IKs to fulfill physiological roles as disparate as cardiac repolarization and the maintenance of endolymph K+ homeostasis, but also to cause significant disease when it malfunctions. Here, we review new areas of understanding in the assembly, kinetics of activation and inactivation, voltage-sensor pore coupling, unitary events and regulation of this important ion channel complex, all of which have been given further impetus by the recent solution of cryo-EM structural representations of KCNQ1 alone and KCNQ1+KCNE3. Recently, the stoichiometric ratio of KCNE1 to KCNQ1 subunits has been confirmed to be variable up to a ratio of 4:4, rather than fixed at 2:4, and we will review the results and new methodologies that support this conclusion. Significant advances have been made in understanding differences between KCNQ1 and IKs gating using voltage clamp fluorimetry and mutational analysis to illuminate voltage sensor activation and inactivation, and the relationship between voltage sensor translation and pore domain opening. We now understand that the KCNQ1 pore can open with different permeabilities and conductance when the voltage sensor is in partially or fully activated positions, and the ability to make robust single channel recordings from IKs channels has also revealed the complicated pore subconductance architecture during these opening steps, during inactivation, and regulation by 1−4 associated KCNE1 subunits. Experiments placing mutations into individual voltage sensors to drastically change voltage dependence or prevent their movement altogether have demonstrated that the activation of KCNQ1 alone and IKs can best be explained using allosteric models of channel gating. Finally, we discuss how the intrinsic gating properties of KCNQ1 and IKs are highly modulated through the impact of intracellular signaling molecules and co-factors such as PIP2, protein kinase A, calmodulin and ATP, all of which modulate IKs current kinetics and contribute to diverse IKs channel complex function.
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Affiliation(s)
- Yundi Wang
- Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, BC, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, BC, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, BC, Canada
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11
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Jalily PH, Duncan MC, Fedida D, Wang J, Tietjen I. Put a cork in it: Plugging the M2 viral ion channel to sink influenza. Antiviral Res 2020; 178:104780. [PMID: 32229237 PMCID: PMC7102647 DOI: 10.1016/j.antiviral.2020.104780] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [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: 10/14/2019] [Revised: 02/12/2020] [Accepted: 03/20/2020] [Indexed: 12/17/2022]
Abstract
The ongoing threat of seasonal and pandemic influenza to human health requires antivirals that can effectively supplement existing vaccination strategies. The M2 protein of influenza A virus (IAV) is a proton-gated, proton-selective ion channel that is required for virus replication and is an established antiviral target. While licensed adamantane-based M2 antivirals have been historically used, M2 mutations that confer major adamantane resistance are now so prevalent in circulating virus strains that these drugs are no longer recommended. Here we review the current understanding of IAV M2 structure and function, mechanisms of inhibition, the rise of drug resistance mutations, and ongoing efforts to develop new antivirals that target resistant forms of M2.
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Affiliation(s)
- Pouria H Jalily
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Maggie C Duncan
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tuscon, AZ, USA
| | - Ian Tietjen
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada; The Wistar Institute, Philadelphia, PA, USA.
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12
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Wang Y, Eldstrom JR, Fedida D. Mefenamic Acid Binding and Effect on I Channel Gating. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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13
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Fedida D, Westhoff MF, Eldstrom JR, Murray CI, Thompson E. IKS Ion-Channel Pore Conductance Can Result from Individual Voltage Sensor Movements. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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14
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Pourrier M, Fedida D. The Emergence of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes (hiPSC-CMs) as a Platform to Model Arrhythmogenic Diseases. Int J Mol Sci 2020; 21:ijms21020657. [PMID: 31963859 PMCID: PMC7013748 DOI: 10.3390/ijms21020657] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [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: 11/30/2019] [Revised: 01/13/2020] [Accepted: 01/15/2020] [Indexed: 12/13/2022] Open
Abstract
There is a need for improved in vitro models of inherited cardiac diseases to better understand basic cellular and molecular mechanisms and advance drug development. Most of these diseases are associated with arrhythmias, as a result of mutations in ion channel or ion channel-modulatory proteins. Thus far, the electrophysiological phenotype of these mutations has been typically studied using transgenic animal models and heterologous expression systems. Although they have played a major role in advancing the understanding of the pathophysiology of arrhythmogenesis, more physiological and predictive preclinical models are necessary to optimize the treatment strategy for individual patients. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have generated much interest as an alternative tool to model arrhythmogenic diseases. They provide a unique opportunity to recapitulate the native-like environment required for mutated proteins to reproduce the human cellular disease phenotype. However, it is also important to recognize the limitations of this technology, specifically their fetal electrophysiological phenotype, which differentiates them from adult human myocytes. In this review, we provide an overview of the major inherited arrhythmogenic cardiac diseases modeled using hiPSC-CMs and for which the cellular disease phenotype has been somewhat characterized.
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Affiliation(s)
- Marc Pourrier
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC V6T 1Z3, Canada;
- IonsGate Preclinical Services Inc., Vancouver, BC V6T 1Z3, Canada
- Correspondence:
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC V6T 1Z3, Canada;
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15
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Wang Y, Eldstrom J, Fedida D. The I Ks Ion Channel Activator Mefenamic Acid Requires KCNE1 and Modulates Channel Gating in a Subunit-Dependent Manner. Mol Pharmacol 2019; 97:132-144. [PMID: 31722973 DOI: 10.1124/mol.119.117952] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 11/04/2019] [Indexed: 01/05/2023] Open
Abstract
The pairing of KCNQ1 and KCNE1 subunits together mediates the cardiac slow delayed rectifier current (I Ks ), which is partly responsible for cardiomyocyte repolarization and physiologic shortening of the cardiac action potential. Mefenamic acid, a nonsteroidal anti-inflammatory drug, has been identified as an I Ks activator. Here, we provide a biophysical and pharmacological characterization of mefenamic acid's effect on I Ks Using whole-cell patch clamp, we show that mefenamic acid enhances I Ks activity in both a dose- and stoichiometry-dependent fashion by changing the slowly activating and deactivating I Ks current into an almost linear current with instantaneous onset and slowed tail current decay, sensitive to the I Ks blocker (3R,4S)-(+)-N-[3-hydroxy-2,2-dimethyl-6-(4,4,4-trifluorobutoxy) chroman-4-yl]-N-methylmethanesulfonamide (HMR1556). Both single channels, which reveal no change in the maximum conductance, and whole-cell studies, which reveal a dramatically altered conductance-voltage relationship despite increasingly longer interpulse intervals, suggest mefenamic acid decreases the voltage sensitivity of the I Ks channel and shifts channel gating kinetics toward more negative potentials. Modeling studies revealed that changes in voltage sensor activation kinetics are sufficient to reproduce the dose and frequency dependence of mefenamic acid action on I Ks channels. Mutational analysis showed that mefenamic acid's effect on I Ks required residue K41 and potentially other surrounding residues on the extracellular surface of KCNE1, and explains why the KCNQ1 channel alone is insensitive to up to 1 mM mefenamic acid. Given that mefenamic acid can enhance all I Ks channel complexes containing different ratios of KCNQ1 to KCNE1, it may provide a promising therapeutic approach to treating life-threatening cardiac arrhythmia syndromes. SIGNIFICANCE STATEMENT: The channels which generate the cardiac slow delayed rectifier K+ current (I Ks ) are composed of KCNQ1 and KCNE1 subunits. Due to the critical role played by I Ks in heartbeat regulation, enhancing I Ks current has been identified as a promising therapeutic strategy to treat various heart rhythm diseases. Most I Ks activators, unfortunately, only work on KCNQ1 alone and not the physiologically relevant I Ks channel. We have demonstrated that mefenamic acid can enhance I Ks in a dose- and stoichiometry-dependent fashion, regulated by its interactions with KCNE1.
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Affiliation(s)
- Yundi Wang
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
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16
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Abstract
The IKs current is important in the heart’s response to sympathetic stimulation. β-adrenergic stimulation increases the amount of IKs and creates a repolarization reserve that shortens the cardiac action potential duration. We have recently shown that 8-CPT-cAMP, a membrane-permeable cAMP analog, changes the channel kinetics and causes it to open more quickly and more often, as well as to higher subconductance levels, which produces an increase in the IKs current. The mechanism proposed to underlie these kinetic changes is increased activation of the voltage sensors. The present study extends our previous work and shows detailed subconductance analysis of the effects of 8-CPT-cAMP on an enhanced gating mutant (S209F) and on a double pseudo-phosphorylated IKs channel (S27D/S92D). 8-CPT-cAMP still produced kinetic changes in S209F + KCNE1, further enhancing gating, while S27D/S92D + KCNE1 showed no significant response to 8-CPT-cAMP, suggesting that these last two mutations fully recapitulate the effect of channel phosphorylation by cAMP.
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Affiliation(s)
- Emely Thompson
- a Department of Anesthesiology, Pharmacology and Therapeutics , University of British Columbia , Vancouver , BC , Canada
| | - Jodene Eldstrom
- a Department of Anesthesiology, Pharmacology and Therapeutics , University of British Columbia , Vancouver , BC , Canada
| | - David Fedida
- a Department of Anesthesiology, Pharmacology and Therapeutics , University of British Columbia , Vancouver , BC , Canada
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17
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Thompson E, Eldstrom J, Westhoff M, McAfee D, Fedida D. The I Ks Channel Response to cAMP Is Modulated by the KCNE1:KCNQ1 Stoichiometry. Biophys J 2018; 115:1731-1740. [PMID: 30314657 DOI: 10.1016/j.bpj.2018.09.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 09/08/2018] [Accepted: 09/20/2018] [Indexed: 12/29/2022] Open
Abstract
The delayed potassium rectifier current, IKs, is assembled from tetramers of KCNQ1 and varying numbers of KCNE1 accessory subunits in addition to calmodulin. This channel complex is important in the response of the cardiac action potential to sympathetic stimulation, during which IKs is enhanced. This is likely due to channels opening more quickly, more often, and to greater sublevel amplitudes during adrenergic stimulation. KCNQ1 alone is unresponsive to cyclic adenosine monophosphate (cAMP), and thus KCNE1 is required for a functional effect of protein kinase A phosphorylation. Here, we investigate the effect that KCNE1 has on the response to 8-4-chlorophenylthio (CPT)-cAMP, a membrane-permeable cAMP analog, by varying the number of KCNE1 subunits present using fusion constructs of IKs with either one (EQQQQ) or two (EQQ) KCNE1 subunits in the channel complex with KCNQ1. These experiments use both whole-cell and single-channel recording techniques. EQQ (2:4, E1:Q1) shows a significant shift in V1/2 of activation from 10.4 mV ± 2.2 in control to -2.7 mV ± 1.2 (p-value: 0.0024). EQQQQ (1:4, E1:Q1) shows a smaller change in response to 8-CPT-cAMP, 6.3 mV ± 2.3 to -3.2 mV ± 3.0 (p-value: 0.0435). As the number of KCNE1 subunits is reduced, the shift in the V1/2 of activation becomes smaller. At the single-channel level, a similar graded change in subconductance occupancy and channel activity is seen in response to 8-CPT-cAMP: the less E1, the smaller the response. However, both constructs show a significant reduction of a similar magnitude in the first latency to opening (EQQ control: 0.90 s ± 0.07 to 0.71 s ± 0.06, p-value: 0.0032 and EQQQQ control: 0.94 s ± 0.09 to 0.56 s ± 0.07, p-value < 0.0001). This suggests that there are both E1-dependent and E1-independent effects of 8-CPT-cAMP on the channel.
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Affiliation(s)
- Emely Thompson
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Donald McAfee
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada.
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18
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19
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Macdonald LC, Kim RY, Kurata HT, Fedida D. Probing the molecular basis of hERG drug block with unnatural amino acids. Sci Rep 2018; 8:289. [PMID: 29321549 PMCID: PMC5762913 DOI: 10.1038/s41598-017-18448-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 12/11/2017] [Indexed: 11/30/2022] Open
Abstract
Repolarization of the cardiac action potential is primarily mediated by two voltage-dependent potassium currents: IKr and IKs. The voltage-gated potassium channel that gives rise to IKr, Kv11.1 (hERG), is uniquely susceptible to high-affinity block by a wide range of drug classes. Pore residues Tyr652 and Phe656 are critical to potent drug interaction with hERG. It is considered that the molecular basis of this broad-spectrum drug block phenomenon occurs through interactions specific to the aromatic nature of the side chains at Tyr652 and Phe656. In this study, we used nonsense suppression to incorporate singly and doubly fluorinated phenylalanine residues at Tyr652 and Phe656 to assess cation-π interactions in hERG terfenadine, quinidine, and dofetilide block. Incorporation of these unnatural amino acids was achieved with minimal alteration to channel activation or inactivation gating. Our assessment of terfenadine, quinidine, and dofetilide block did not reveal evidence of a cation-π interaction at either aromatic residue, but, interestingly, shows that certain fluoro-Phe substitutions at position 652 result in weaker drug potency.
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Affiliation(s)
- Logan C Macdonald
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Robin Y Kim
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Harley T Kurata
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
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20
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Westhoff M, Murray CI, Eldstrom J, Fedida D. Photo-Cross-Linking of I Ks Demonstrates State-Dependent Interactions between KCNE1 and KCNQ1. Biophys J 2017; 113:415-425. [PMID: 28746852 DOI: 10.1016/j.bpj.2017.06.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 05/26/2017] [Accepted: 06/02/2017] [Indexed: 01/09/2023] Open
Abstract
The slow delayed rectifier potassium current (IKs) is a key repolarizing current during the cardiac action potential. It consists of four KCNQ1 α-subunits and up to four KCNE1 β-subunits, which are thought to reside within external clefts of the channel. The interaction of KCNE1 with KCNQ1 dramatically delays opening of the channel but the mechanisms by which this occur are not yet fully understood. Here, we have used unnatural amino acid photo-cross-linking to investigate the dynamic interactions that occur between KCNQ1 and KCNE1 during activation gating. The unnatural amino acid p-Benzoylphenylalanine was successfully incorporated into two residues within the transmembrane domain of KCNE1: F56 and F57. UV-induced cross-linking suggested that F56Bpa interacts with KCNQ1 in the open state, whereas F57Bpa interacts predominantly in resting channel conformations. When UV was applied at progressively more depolarized preopen holding potentials, cross-linking of F57Bpa with KCNQ1 was slowed, which indicates that KCNE1 is displaced within the channel's cleft early during activation, or that conformational changes in KCNQ1 alter its interaction with KCNE1. In E1R/R4E KCNQ1, a mutant with constitutively activated voltage sensors, F56Bpa and F57Bpa KCNE1 were cross-linked in open and closed states, respectively, which suggests that their actions are mediated mainly by modulation of KCNQ1 pore function.
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Affiliation(s)
- Maartje Westhoff
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher I Murray
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada.
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21
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Thompson E, Eldstrom J, Westhoff M, McAfee D, Balse E, Fedida D. cAMP-dependent regulation of IKs single-channel kinetics. J Gen Physiol 2017; 149:781-798. [PMID: 28687606 PMCID: PMC5560775 DOI: 10.1085/jgp.201611734] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 06/20/2017] [Indexed: 02/06/2023] Open
Abstract
The delayed potassium rectifier current, IKs , is composed of KCNQ1 and KCNE1 subunits and plays an important role in cardiac action potential repolarization. During β-adrenergic stimulation, 3'-5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) phosphorylates KCNQ1, producing an increase in IKs current and a shortening of the action potential. Here, using cell-attached macropatches and single-channel recordings, we investigate the microscopic mechanisms underlying the cAMP-dependent increase in IKs current. A membrane-permeable cAMP analog, 8-(4-chlorophenylthio)-cAMP (8-CPT-cAMP), causes a marked leftward shift of the conductance-voltage relation in macropatches, with or without an increase in current size. Single channels exhibit fewer silent sweeps, reduced first latency to opening (control, 1.61 ± 0.13 s; cAMP, 1.06 ± 0.11 s), and increased higher-subconductance-level occupancy in the presence of cAMP. The E160R/R237E and S209F KCNQ1 mutants, which show fixed and enhanced voltage sensor activation, respectively, largely abolish the effect of cAMP. The phosphomimetic KCNQ1 mutations, S27D and S27D/S92D, are much less and not at all responsive, respectively, to the effects of PKA phosphorylation (first latency of S27D + KCNE1 channels: control, 1.81 ± 0.1 s; 8-CPT-cAMP, 1.44 ± 0.1 s, P < 0.05; latency of S27D/S92D + KCNE1: control, 1.62 ± 0.1 s; cAMP, 1.43 ± 0.1 s, nonsignificant). Using total internal reflection fluorescence microscopy, we find no overall increase in surface expression of the channel during exposure to 8-CPT-cAMP. Our data suggest that the cAMP-dependent increase in IKs current is caused by an increase in the likelihood of channel opening, combined with faster openings and greater occupancy of higher subconductance levels, and is mediated by enhanced voltage sensor activation.
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Affiliation(s)
- Emely Thompson
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Donald McAfee
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Elise Balse
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 1166, Unité de recherche sur les maladies cardiovasculaires, le métabolisme et la nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, Paris, France
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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22
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Pourier M, Kettenhofen R, Gibson J, Luerman G, Fedida D, Bohlen H. The late sodium current participates in repolarization of hiPSC-derived cardiac myocytes. J Pharmacol Toxicol Methods 2017. [DOI: 10.1016/j.vascn.2017.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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23
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Tzitzoglaki C, Wright A, Freudenberger K, Hoffmann A, Tietjen I, Stylianakis I, Kolarov F, Fedida D, Schmidtke M, Gauglitz G, Cross TA, Kolocouris A. Binding and Proton Blockage by Amantadine Variants of the Influenza M2WT and M2S31N Explained. J Med Chem 2017; 60:1716-1733. [DOI: 10.1021/acs.jmedchem.6b01115] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Christina Tzitzoglaki
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
| | - Anna Wright
- Institute
of Molecular Biophysics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
| | - Kathrin Freudenberger
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - Anja Hoffmann
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Strasse 2, D-07745 Jena, Germany
| | - Ian Tietjen
- Department
of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Ioannis Stylianakis
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
| | - Felix Kolarov
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - David Fedida
- Department
of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michaela Schmidtke
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Strasse 2, D-07745 Jena, Germany
| | - Günter Gauglitz
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - Timothy A. Cross
- Institute
of Molecular Biophysics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
- Department
of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Antonios Kolocouris
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
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24
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Bround MJ, Wambolt R, Cen H, Asghari P, Albu RF, Han J, McAfee D, Pourrier M, Scott NE, Bohunek L, Kulpa JE, Chen SRW, Fedida D, Brownsey RW, Borchers CH, Foster LJ, Mayor T, Moore EDW, Allard MF, Johnson JD. Cardiac Ryanodine Receptor (Ryr2)-mediated Calcium Signals Specifically Promote Glucose Oxidation via Pyruvate Dehydrogenase. J Biol Chem 2016; 291:23490-23505. [PMID: 27621312 DOI: 10.1074/jbc.m116.756973] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Indexed: 11/06/2022] Open
Abstract
Cardiac ryanodine receptor (Ryr2) Ca2+ release channels and cellular metabolism are both disrupted in heart disease. Recently, we demonstrated that total loss of Ryr2 leads to cardiomyocyte contractile dysfunction, arrhythmia, and reduced heart rate. Acute total Ryr2 ablation also impaired metabolism, but it was not clear whether this was a cause or consequence of heart failure. Previous in vitro studies revealed that Ca2+ flux into the mitochondria helps pace oxidative metabolism, but there is limited in vivo evidence supporting this concept. Here, we studied heart-specific, inducible Ryr2 haploinsufficient (cRyr2Δ50) mice with a stable 50% reduction in Ryr2 protein. This manipulation decreased the amplitude and frequency of cytosolic and mitochondrial Ca2+ signals in isolated cardiomyocytes, without changes in cardiomyocyte contraction. Remarkably, in the context of well preserved contractile function in perfused hearts, we observed decreased glucose oxidation, but not fat oxidation, with increased glycolysis. cRyr2Δ50 hearts exhibited hyperphosphorylation and inhibition of pyruvate dehydrogenase, the key Ca2+-sensitive gatekeeper to glucose oxidation. Metabolomic, proteomic, and transcriptomic analyses revealed additional functional networks associated with altered metabolism in this model. These results demonstrate that Ryr2 controls mitochondrial Ca2+ dynamics and plays a specific, critical role in promoting glucose oxidation in cardiomyocytes. Our findings indicate that partial RYR2 loss is sufficient to cause metabolic abnormalities seen in heart disease.
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Affiliation(s)
- Michael J Bround
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Rich Wambolt
- From the Cardiovascular Research Group, Life Sciences Institute and.,the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | - Haoning Cen
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Parisa Asghari
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Razvan F Albu
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Jun Han
- the University of Victoria-Genome British Columbia Proteomics Centre, Victoria, British Columbia V8Z 7X8, and
| | - Donald McAfee
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | - Marc Pourrier
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | - Nichollas E Scott
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Lubos Bohunek
- the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | | | - S R Wayne Chen
- the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 2T9, Canada
| | - David Fedida
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | | | - Christoph H Borchers
- the University of Victoria-Genome British Columbia Proteomics Centre, Victoria, British Columbia V8Z 7X8, and
| | - Leonard J Foster
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Thibault Mayor
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Edwin D W Moore
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Michael F Allard
- From the Cardiovascular Research Group, Life Sciences Institute and.,the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | - James D Johnson
- From the Cardiovascular Research Group, Life Sciences Institute and .,Departments of Cellular and Physiological Sciences
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25
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Fedida D, Macdonald L. hERG long QT syndrome type 2 mutants need more than a chaperone to dance. J Physiol 2016; 594:4095-6. [DOI: 10.1113/jp272417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics; University of British Columbia; 2350 Health Sciences Mall Vancouver British Columbia Canada V6T 1Z3
| | - Logan Macdonald
- Department of Anesthesiology, Pharmacology and Therapeutics; University of British Columbia; 2350 Health Sciences Mall Vancouver British Columbia Canada V6T 1Z3
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26
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Rezazadeh S, Hesketh JC, Fedida D. Rb+ Flux through hERG Channels Affects the Potency of Channel Blocking Drugs: Correlation with Data Obtained Using a High-Throughput Rb+ Efflux Assay. ACTA ACUST UNITED AC 2016; 9:588-97. [PMID: 15475478 DOI: 10.1177/1087057104264798] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The nonradioactive Rb+ efflux assay has become a reliable and efficient high-throughput hERG screening method, but it is limited by its low sensitivity for potent hERG blockers. Using the patch clamp technique, the authors found that the low sensitivity is due in part to the use of Rb+ as the permeating cation in the assay. The affinities of the drugs measured by patch clamp technique in the presence of Rb+ were 3- to 10-fold lower than when measured by the same method in the presence of K+ ions. The apparent affinity of the drugs decreased even further when monitored bytheRb+ efflux assay. It was also observed that Rb+ had minimal effects on the activation properties of channels while there was a significant change in the half-inactivation potential. This voltage shift reduces hERG channel inactivation at efflux assay potentials, and will reduce the affinity of hERG-blocking drugs that bind to inactivated states of the channel. In combination with the effects of elevated extracellular ion concentrations, it is likely that Rb+ modulation of hERG channel inactivation is largely responsible for the reduced drug potencies observed in the Rb+ efflux assay.
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Affiliation(s)
- Saman Rezazadeh
- Department of Physiology, University of British Columbia, Vancouver, BC, Canada
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Moral-Sanz J, Mahmoud AD, Ross FA, Eldstrom J, Fedida D, Hardie DG, Evans AM. AMP-activated protein kinase inhibits Kv 1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation. J Physiol 2016; 594:4901-15. [PMID: 27062501 PMCID: PMC5009768 DOI: 10.1113/jp272032] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 03/26/2016] [Indexed: 12/29/2022] Open
Abstract
Key points Progression of hypoxic pulmonary hypertension is thought to be due, in part, to suppression of voltage‐gated potassium channels (Kv) in pulmonary arterial smooth muscle by hypoxia, although the precise molecular mechanisms have been unclear. AMP‐activated protein kinase (AMPK) has been proposed to couple inhibition of mitochondrial metabolism by hypoxia to acute hypoxic pulmonary vasoconstriction and progression of pulmonary hypertension. Inhibition of complex I of the mitochondrial electron transport chain activated AMPK and inhibited Kv1.5 channels in pulmonary arterial myocytes. AMPK activation by 5‐aminoimidazole‐4‐carboxamide riboside, A769662 or C13 attenuated Kv1.5 currents in pulmonary arterial myocytes, and this effect was non‐additive with respect to Kv1.5 inhibition by hypoxia and mitochondrial poisons. Recombinant AMPK phosphorylated recombinant human Kv1.5 channels in cell‐free assays, and inhibited K+ currents when introduced into HEK 293 cells stably expressing Kv1.5. These results suggest that AMPK is the primary mediator of reductions in Kv1.5 channels following inhibition of mitochondrial oxidative phosphorylation during hypoxia and by mitochondrial poisons.
Abstract Progression of hypoxic pulmonary hypertension is thought to be due, in part, to suppression of voltage‐gated potassium channels (Kv) in pulmonary arterial smooth muscle cells that is mediated by the inhibition of mitochondrial oxidative phosphorylation. We sought to determine the role in this process of the AMP‐activated protein kinase (AMPK), which is intimately coupled to mitochondrial function due to its activation by LKB1‐dependent phosphorylation in response to increases in the cellular AMP:ATP and/or ADP:ATP ratios. Inhibition of complex I of the mitochondrial electron transport chain using phenformin activated AMPK and inhibited Kv currents in pulmonary arterial myocytes, consistent with previously reported effects of mitochondrial inhibitors. Myocyte Kv currents were also markedly inhibited upon AMPK activation by A769662, 5‐aminoimidazole‐4‐carboxamide riboside and C13 and by intracellular dialysis from a patch‐pipette of activated (thiophosphorylated) recombinant AMPK heterotrimers (α2β2γ1 or α1β1γ1). Hypoxia and inhibitors of mitochondrial oxidative phosphorylation reduced AMPK‐sensitive K+ currents, which were also blocked by the selective Kv1.5 channel inhibitor diphenyl phosphine oxide‐1 but unaffected by the presence of the BKCa channel blocker paxilline. Moreover, recombinant human Kv1.5 channels were phosphorylated by AMPK in cell‐free assays, and K+ currents carried by Kv1.5 stably expressed in HEK 293 cells were inhibited by intracellular dialysis of AMPK heterotrimers and by A769662, the effects of which were blocked by compound C. We conclude that AMPK mediates Kv channel inhibition by hypoxia in pulmonary arterial myocytes, at least in part, through phosphorylation of Kv1.5 and/or an associated protein. Progression of hypoxic pulmonary hypertension is thought to be due, in part, to suppression of voltage‐gated potassium channels (Kv) in pulmonary arterial smooth muscle by hypoxia, although the precise molecular mechanisms have been unclear. AMP‐activated protein kinase (AMPK) has been proposed to couple inhibition of mitochondrial metabolism by hypoxia to acute hypoxic pulmonary vasoconstriction and progression of pulmonary hypertension. Inhibition of complex I of the mitochondrial electron transport chain activated AMPK and inhibited Kv1.5 channels in pulmonary arterial myocytes. AMPK activation by 5‐aminoimidazole‐4‐carboxamide riboside, A769662 or C13 attenuated Kv1.5 currents in pulmonary arterial myocytes, and this effect was non‐additive with respect to Kv1.5 inhibition by hypoxia and mitochondrial poisons. Recombinant AMPK phosphorylated recombinant human Kv1.5 channels in cell‐free assays, and inhibited K+ currents when introduced into HEK 293 cells stably expressing Kv1.5. These results suggest that AMPK is the primary mediator of reductions in Kv1.5 channels following inhibition of mitochondrial oxidative phosphorylation during hypoxia and by mitochondrial poisons.
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Affiliation(s)
- Javier Moral-Sanz
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Amira D Mahmoud
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Fiona A Ross
- Division of Cell Signalling & Immunology, School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Jodene Eldstrom
- Department of Anaesthesiology. Pharmacology and Therapeutics, University of British Columbia, 2350 Health Science Mall, Vancouver, Canada, V6T 1Z3
| | - David Fedida
- Department of Anaesthesiology. Pharmacology and Therapeutics, University of British Columbia, 2350 Health Science Mall, Vancouver, Canada, V6T 1Z3
| | - D Grahame Hardie
- Division of Cell Signalling & Immunology, School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - A Mark Evans
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh, EH8 9XD, UK
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Jalily PH, Eldstrom J, Miller SC, Kwan DC, Tai SSH, Chou D, Niikura M, Tietjen I, Fedida D. Mechanisms of Action of Novel Influenza A/M2 Viroporin Inhibitors Derived from Hexamethylene Amiloride. Mol Pharmacol 2016; 90:80-95. [PMID: 27193582 DOI: 10.1124/mol.115.102731] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 05/12/2016] [Indexed: 01/09/2023] Open
Abstract
The increasing prevalence of influenza viruses with resistance to approved antivirals highlights the need for new anti-influenza therapeutics. Here we describe the functional properties of hexamethylene amiloride (HMA)-derived compounds that inhibit the wild-type and adamantane-resistant forms of the influenza A M2 ion channel. For example, 6-(azepan-1-yl)-N-carbamimidoylnicotinamide ( 9: ) inhibits amantadine-sensitive M2 currents with 3- to 6-fold greater potency than amantadine or HMA (IC50 = 0.2 vs. 0.6 and 1.3 µM, respectively). Compound 9: competes with amantadine for M2 inhibition, and molecular docking simulations suggest that 9: binds at site(s) that overlap with amantadine binding. In addition, tert-butyl 4'-(carbamimidoylcarbamoyl)-2',3-dinitro-[1,1'-biphenyl]-4-carboxylate ( 27: ) acts both on adamantane-sensitive and a resistant M2 variant encoding a serine to asparagine 31 mutation (S31N) with improved efficacy over amantadine and HMA (IC50 = 0.6 µM and 4.4 µM, respectively). Whereas 9: inhibited in vitro replication of influenza virus encoding wild-type M2 (EC50 = 2.3 µM), both 27: and tert-butyl 4'-(carbamimidoylcarbamoyl)-2',3-dinitro-[1,1'-biphenyl]-4-carboxylate ( 26: ) preferentially inhibited viruses encoding M2(S31N) (respective EC50 = 18.0 and 1.5 µM). This finding indicates that HMA derivatives can be designed to inhibit viruses with resistance to amantadine. Our study highlights the potential of HMA derivatives as inhibitors of drug-resistant influenza M2 ion channels.
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Affiliation(s)
- Pouria H Jalily
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Scott C Miller
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Daniel C Kwan
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Sheldon S-H Tai
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Doug Chou
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Masahiro Niikura
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Ian Tietjen
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
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Goodchild SJ, Macdonald LC, Fedida D. Sequence of gating charge movement and pore gating in HERG activation and deactivation pathways. Biophys J 2016; 108:1435-1447. [PMID: 25809256 DOI: 10.1016/j.bpj.2015.02.014] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/08/2015] [Accepted: 02/18/2015] [Indexed: 12/26/2022] Open
Abstract
KV11.1 voltage-gated K(+) channels are noted for unusually slow activation, fast inactivation, and slow deactivation kinetics, which tune channel activity to provide vital repolarizing current during later stages of the cardiac action potential. The bulk of charge movement in human ether-a-go-go-related gene (hERG) is slow, as is return of charge upon repolarization, suggesting that the rates of hERG channel opening and, critically, that of deactivation might be determined by slow voltage sensor movement, and also by a mode-shift after activation. To test these ideas, we compared the kinetics and voltage dependence of ionic activation and deactivation with gating charge movement. At 0 mV, gating charge moved ∼threefold faster than ionic current, which suggests the presence of additional slow transitions downstream of charge movement in the physiological activation pathway. A significant voltage sensor mode-shift was apparent by 24 ms at +60 mV in gating currents, and return of charge closely tracked pore closure after pulses of 100 and 300 ms duration. A deletion of the N-terminus PAS domain, mutation R4AR5A or the LQT2-causing mutation R56Q gave faster-deactivating channels that displayed an attenuated mode-shift of charge. This indicates that charge movement is perturbed by N- and C-terminus interactions, and that these domain interactions stabilize the open state and limit the rate of charge return. We conclude that slow on-gating charge movement can only partly account for slow hERG ionic activation, and that the rate of pore closure has a limiting role in the slow return of gating charges.
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Affiliation(s)
- Samuel J Goodchild
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Logan C Macdonald
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada.
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Capmas P, Pourcelot AG, Giral E, Fedida D, Fernandez H. Office hysteroscopy: A report of 2402 cases. ACTA ACUST UNITED AC 2016; 45:445-50. [DOI: 10.1016/j.jgyn.2016.02.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 02/08/2016] [Accepted: 02/24/2016] [Indexed: 11/15/2022]
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Macdonald L, Kim RY, Kurata HT, Ahern C, Fedida D. Using Unnatural Amino Acids to Probe the Molecular Basis for Herg Drug Block. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Westhoff MF, Murray CI, Thompson E, Emes R, Eldstrom J, Fedida D. Insertion of Crosslinkable Amino Acids into the IKS Channel Complex Demonstrates a Variable KCNQ1:KCNE1 Stoichiometry of up to 4:4. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Murray CI, Westhoff M, Eldstrom J, Thompson E, Emes R, Fedida D. Unnatural amino acid photo-crosslinking of the IKs channel complex demonstrates a KCNE1:KCNQ1 stoichiometry of up to 4:4. eLife 2016; 5. [PMID: 26802629 PMCID: PMC4807126 DOI: 10.7554/elife.11815] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [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: 09/24/2015] [Accepted: 01/22/2016] [Indexed: 12/20/2022] Open
Abstract
Cardiac repolarization is determined in part by the slow delayed rectifier current (IKs), through the tetrameric voltage-gated ion channel, KCNQ1, and its β-subunit, KCNE1. The stoichiometry between α and β-subunits has been controversial with studies reporting either a strict 2 KCNE1:4 KCNQ1 or a variable ratio up to 4:4. We used IKs fusion proteins linking KCNE1 to one (EQ), two (EQQ) or four (EQQQQ) KCNQ1 subunits, to reproduce compulsory 4:4, 2:4 or 1:4 stoichiometries. Whole cell and single-channel recordings showed EQQ and EQQQQ to have increasingly hyperpolarized activation, reduced conductance, and shorter first latency of opening compared to EQ - all abolished by the addition of KCNE1. As well, using a UV-crosslinking unnatural amino acid in KCNE1, we found EQQQQ and EQQ crosslinking rates to be progressively slowed compared to KCNQ1, which demonstrates that no intrinsic mechanism limits the association of up to four β-subunits within the IKs complex. DOI:http://dx.doi.org/10.7554/eLife.11815.001 The membrane that surrounds heart muscle cells contains specialized channels that can open and close to control the movements of charged ions into and out of the cell. This ion flow generates the electrical signals that stimulate the heart muscle to contract for each heart beat. Different ion channels influence different steps in the initiation and termination of each electrical signal. For example, the IKs ion channel complex helps to return the cell to a resting state so the heart muscle can relax. This allows chambers of the heart to fill with blood before the next beat pumps blood throughout the body. Mutations that affect IKs cause serious heart conditions that affect heart rhythm, such as Long QT Syndrome. The IKs complex consists of channels that are each made of four copies of a protein called KCNQ1, through which potassium ions exit the cell. This channel opens in response to changes in the voltage across the cell membrane (known as the “membrane potential”). A small protein subunit called KCNE1 also makes up part of the complex, but it was not clear how many KCNE1 molecules combine with KCNQ1 to form a working channel complex. Several previous studies have reported two different results: that the KCNQ1 channel complex only exists with two KCNE1 molecules, or that the association is flexible, allowing the complex to contain up to four KCNE1 subunits. Murray et al. have now constructed IKs fusion channels out of different numbers of KCNQ1 and KCNE1 molecules to investigate how different KCNQ1:KCNE1 ratios affect how the channel works. Measuring the responses of these modified channels in mammalian cells revealed that channels with four KCNE1 subunits conducted ions better than channels with one or two KCNE1s. The channels containing fewer KCNE1s also opened at lower membrane potentials and after a shorter delay following a change in the membrane potential. Further experiments also supported the theory that up to four independent KCNE1 subunits may be easily added to the IKs ion channel complex. Murray et al. suggest that by being able to form channel complexes containing different numbers of KCNE1 subunits, cells can more flexibly control the rate at which ions flow out of the heart cells to tune the electrical signals that trigger each heart beat. The next challenges will be to determine the composition of the IKs channel complex in adult heart cells and to investigate how the complex might change with disease. DOI:http://dx.doi.org/10.7554/eLife.11815.002
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Affiliation(s)
- Christopher I Murray
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Emely Thompson
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Robert Emes
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
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Wang L, Meng X, Yuchi Z, Zhao Z, Xu D, Fedida D, Wang Z, Huang C. De Novo Mutation in the SCN5A Gene Associated with Brugada Syndrome. Cell Physiol Biochem 2015; 36:2250-62. [PMID: 26279430 DOI: 10.1159/000430189] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/12/2015] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Brugada syndrome (BrS) is a genetically determined cardiac electrical disorder, characterized by typical electrocardiography (ECG) alterations, and it is an arrhythmogenic syndrome that may lead to sudden cardiac death. The most common genotype found among BrS patients is caused by mutations in the SCN5A gene, which lead to a loss of function of the cardiac sodium (Na(+)) channel (Nav1.5) by different mechanisms. METHODS The assay of confocal laser microscopy and western blot were used to identify the expression and location of L812Q at the cell surface. Characterization of Nav1.5 L812Q mutant Na(+) channels was text by patch-clamp recordings, and the PHYRE2 server was used to build a model for human Nav1.5 channel. RESULTS Here, we report that a novel missense SCN5A mutation, L812Q, localized in the DII-S4 transmembrane region of the Nav1.5 channel protein, was identified in an index patient who showed a typical BrS type-1 ECG phenotype. The mutation was absent in the patient's parents and brother. Heterologous expression of the wild-type (WT) and L812Q mutant Nav1.5 channels in human embryonic kidney cells (HEK293 cells) reveals that the mutation results in a reduction of Na(+) current density as well as ∼20 mV hyperpolarizing shift of the voltage dependence of inactivation. The voltage dependence of activation and the time course for recovery from inactivation are not affected by the mutation. The hyperpolarizing shift of the voltage dependence of inactivation caused a reduction of the Na(+) window current as well. In addition, western blot and confocal laser microscopy imaging experiments showed that the mutation causes fewer channel to be expressed at the membrane than WT channel. A large proportion of the mutant channels are retained in the cytoplasm, probably in the endoplasmic reticulum. CONCLUSION The decrease of channel expression, hyperpolarizing shift of voltage dependence of inactivation, and a decline of Na(+) window current caused by L812Q mutation lead to a reduction of Na(+) current during the upstroke and the repolarization phases of cardiac action potential, which contribute to the development of BrS.
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Affiliation(s)
- Lumin Wang
- Department of Cell Biology and Genetics, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, P.R.China
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Tietjen I, Ntie-Kang F, Mwimanzi P, Onguéné PA, Scull MA, Idowu TO, Ogundaini AO, Meva’a LM, Abegaz BM, Rice CM, Andrae-Marobela K, Brockman MA, Brumme ZL, Fedida D. Screening of the Pan-African natural product library identifies ixoratannin A-2 and boldine as novel HIV-1 inhibitors. PLoS One 2015; 10:e0121099. [PMID: 25830320 PMCID: PMC4382154 DOI: 10.1371/journal.pone.0121099] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/09/2015] [Indexed: 11/29/2022] Open
Abstract
The continued burden of HIV in resource-limited regions such as parts of sub-Saharan Africa, combined with adverse effects and potential risks of resistance to existing antiretroviral therapies, emphasize the need to identify new HIV inhibitors. Here we performed a virtual screen of molecules from the pan-African Natural Product Library, the largest collection of medicinal plant-derived pure compounds on the African continent. We identified eight molecules with structural similarity to reported interactors of Vpu, an HIV-1 accessory protein with reported ion channel activity. Using in vitro HIV-1 replication assays with a CD4+ T cell line and peripheral blood mononuclear cells, we confirmed antiviral activity and minimal cytotoxicity for two compounds, ixoratannin A-2 and boldine. Notably, ixoratannin A-2 retained inhibitory activity against recombinant HIV-1 strains encoding patient-derived mutations that confer resistance to protease, non-nucleoside reverse transcriptase, or integrase inhibitors. Moreover, ixoratannin A-2 was less effective at inhibiting replication of HIV-1 lacking Vpu, supporting this protein as a possible direct or indirect target. In contrast, boldine was less effective against a protease inhibitor-resistant HIV-1 strain. Both ixoratannin A-2 and boldine also inhibited in vitro replication of hepatitis C virus (HCV). However, BIT-225, a previously-reported Vpu inhibitor, demonstrated antiviral activity but also cytotoxicity in HIV-1 and HCV replication assays. Our work identifies pure compounds derived from African plants with potential novel activities against viruses that disproportionately afflict resource-limited regions of the world.
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Affiliation(s)
- Ian Tietjen
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
- * E-mail: (IT)
| | - Fidele Ntie-Kang
- Department of Chemistry, Chemical and Bioactivity Information Centre, Faculty of Science, University of Buea, Buea, Cameroon
| | - Philip Mwimanzi
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Pascal Amoa Onguéné
- Department of Chemistry, Faculty of Science, University of Douala, Douala, Cameroon
| | - Margaret A. Scull
- Laboratory of Virology and Infectious Disease, The Rockefeller University, New York, NY, United States of America
| | - Thomas Oyebode Idowu
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Abiodun Oguntuga Ogundaini
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Luc Mbaze Meva’a
- Department of Chemistry, Faculty of Science, University of Douala, Douala, Cameroon
| | | | - Charles M. Rice
- Laboratory of Virology and Infectious Disease, The Rockefeller University, New York, NY, United States of America
| | | | - Mark A. Brockman
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
- Department of Molecular Biology and Biochemistry, Faculty of Science, Simon Fraser University, Burnaby, BC, Canada
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada
| | - Zabrina L. Brumme
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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Eldstrom J, Wang Z, Werry D, Wong N, Fedida D. Microscopic mechanisms for long QT syndrome type 1 revealed by single-channel analysis of I(Ks) with S3 domain mutations in KCNQ1. Heart Rhythm 2014; 12:386-94. [PMID: 25444851 DOI: 10.1016/j.hrthm.2014.10.029] [Citation(s) in RCA: 18] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Indexed: 10/24/2022]
Abstract
BACKGROUND The slowly activating delayed rectifier current IKs participates in cardiac repolarization, particularly at high heart rates, and mutations in this K(+) channel complex underlie long QT syndrome (LQTS) types 1 and 5. OBJECTIVE The purpose of this study was to determine biophysical mechanisms of LQT1 through single-channel kinetic analysis of IKs carrying LQT1 mutations in the S3 transmembrane region of the pore-forming subunit KCNQ1. METHODS We analyzed cell-attached recordings from mammalian cells in which a single active KCNQ1 (wild type or mutant) and KCNE1 complex could be detected. RESULTS The S3 mutants of KCNQ1 studied (D202H, I204F, V205M, and S209F), with the exception of S209F, all led to a reduction in channel activity through distinct kinetic mechanisms. D202H, I204F, and V205M showed decreased open probability (Po) compared with wild type (0.07, 0.04, and 0.12 vs 0.2); increased first latency from 1.66 to >2 seconds at +60 mV (I204F, V205M); variable-to-severe reductions in open dwell times (≥50% in V205M); stabilization of closed states (D202H); and an inability of channels to reach full conductance levels (V205M, I204F). S209F is a kinetic gain-of-function mutation with a high Po (0.40) and long open-state dwell times. CONCLUSION S3 mutations in KCNQ1 cause diverse kinetic defects in I(Ks), affecting opening and closing properties, and can account for LQT1 phenotypes.
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Affiliation(s)
- Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Zhuren Wang
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Daniel Werry
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Nathan Wong
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada.
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Peters CJ, Vaid M, Horne AJ, Fedida D, Accili EA. The molecular basis for the actions of KVβ1.2 on the opening and closing of the KV1.2 delayed rectifier channel. Channels (Austin) 2014; 3:314-22. [DOI: 10.4161/chan.3.5.9558] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Mwimanzi PM, Tietjen I, Shahid A, Miller SC, Fedida D, Brummer Z, Brockman M. Identification of a Novel Acylguanidine-based Inhibitor of HIV-1 Replication. AIDS Res Hum Retroviruses 2014. [DOI: 10.1089/aid.2014.5444.abstract] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Philip M. Mwimanzi
- Simon Fraser University, Faculty of Health Sciences, Burnaby, BC, Canada
| | - Ian Tietjen
- University of British Columbia, Vancouver, BC, Canada
| | - Aniqa Shahid
- Simon Fraser University, Faculty of Health Sciences, Burnaby, BC, Canada
| | | | - David Fedida
- University of British Columbia, Vancouver, BC, Canada
| | - Zabrin Brummer
- Simon Fraser University, Faculty of Health Sciences, Burnaby, BC, Canada
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada
| | - Mark Brockman
- Simon Fraser University, Faculty of Health Sciences, Burnaby, BC, Canada
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada
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Pourrier M, Williams S, McAfee D, Belardinelli L, Fedida D. CrossTalk proposal: The late sodium current is an important player in the development of diastolic heart failure (heart failure with a preserved ejection fraction). J Physiol 2014; 592:411-4. [PMID: 24488066 DOI: 10.1113/jphysiol.2013.262261] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Kolocouris A, Tzitzoglaki C, Johnson FB, Zell R, Wright AK, Cross TA, Tietjen I, Fedida D, Busath DD. Aminoadamantanes with persistent in vitro efficacy against H1N1 (2009) influenza A. J Med Chem 2014; 57:4629-39. [PMID: 24793875 PMCID: PMC4127532 DOI: 10.1021/jm500598u] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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A series of 2-adamantanamines with
alkyl adducts of various lengths
were examined for efficacy against strains of influenza A including
those having an S31N mutation in M2 proton channel that confer resistance
to amantadine and rimantadine. The addition of as little as one CH2 group to the methyl adduct of the amantadine/rimantadine
analogue, 2-methyl-2-aminoadamantane, led to activity in vitro against
two M2 S31N viruses A/Calif/07/2009 (H1N1) and A/PR/8/34 (H1N1) but
not to a third A/WS/33 (H1N1). Solid state NMR of the transmembrane
domain (TMD) with a site mutation corresponding to S31N shows evidence
of drug binding. But electrophysiology using the full length S31N
M2 protein in HEK cells showed no blockade. A wild type strain, A/Hong
Kong/1/68 (H3N2) developed resistance to representative drugs within
one passage with mutations in M2 TMD, but A/Calif/07/2009 S31N was
slow (>8 passages) to develop resistance in vitro, and the resistant
virus had no mutations in M2 TMD. The results indicate that 2-alkyl-2-aminoadamantane
derivatives with sufficient adducts can persistently block p2009 influenza
A in vitro through an alternative mechanism. The observations of an
HA1 mutation, N160D, near the sialic acid binding site in both 6-resistant A/Calif/07/2009(H1N1) and the broadly resistant
A/WS/33(H1N1) and of an HA1 mutation, I325S, in the 6-resistant virus at a cell-culture stable site suggest that the drugs
tested here may block infection by direct binding near these critical
sites for virus entry to the host cell.
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Affiliation(s)
- Antonios Kolocouris
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens , Athens 15771, Greece
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Pourrier M, Williams S, McAfee D, Belardinelli L, Fedida D. Rebuttal from Marc Pourrier, Sarah Williams, Donald McAfee, Luiz Belardinelli and David Fedida. J Physiol 2014; 592:419. [DOI: 10.1113/jphysiol.2013.268896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Marc Pourrier
- Department of Anesthesiology; Pharmacology and Therapeutics; University of British Columbia; Vancouver British Columbia Canada
| | - Sarah Williams
- Department of Anesthesiology; Pharmacology and Therapeutics; University of British Columbia; Vancouver British Columbia Canada
| | - Donald McAfee
- Department of Anesthesiology; Pharmacology and Therapeutics; University of British Columbia; Vancouver British Columbia Canada
| | - Luiz Belardinelli
- Department of Biology; Cardiovascular Therapeutic Area; Gilead Sciences; Foster City CA USA
| | - David Fedida
- Department of Anesthesiology; Pharmacology and Therapeutics; University of British Columbia; Vancouver British Columbia Canada
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Abstract
Diastolic dysfunction can lead to heart failure with preserved ejection fraction, for which there is no effective therapeutic. Ranolazine has been reported to reduce diastolic dysfunction, but the specific mechanisms of action are unclear. The effect of ranolazine on diastolic function was examined in spontaneously hypertensive rats (SHRs), where left ventricular relaxation is impaired and stiffness increased. The objective of this study was to determine whether ranolazine improves diastolic function in SHRs and identify the mechanism(s) by which improvement is achieved. Specifically, to test the hypothesis that ranolazine, by inhibiting late sodium current, reduces Ca(2+) overload and promotes ventricular relaxation and reduction in diastolic stiffness, the effects of ranolazine or vehicle on heart function and the response to dobutamine challenge were evaluated in aged male SHRs and Wistar-Kyoto rats by echocardiography and pressure-volume loop analysis. The effects of ranolazine and the more specific sodium channel inhibitor tetrodotoxin were determined on the late sodium current, sarcomere length, and intracellular calcium in isolated cardiomyocytes. Ranolazine reduced the end-diastolic pressure-volume relationship slope and improved diastolic function during dobutamine challenge in the SHR. Ranolazine and tetrodotoxin also enhanced cardiomyocyte relaxation and reduced myoplasmic free Ca(2+) during diastole at high-stimulus rates in the SHR. The density of the late sodium current was elevated in SHRs. In conclusion, ranolazine was effective in reducing diastolic dysfunction in the SHR. Its mechanism of action, at least in part, is consistent with inhibition of the increased late sodium current in the SHR leading to reduced Ca(2+) overload.
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Affiliation(s)
- Sarah Williams
- Department of Anesthesiology, Pharmacology, and Therapeutics, Life Sciences Institute, University of British Columbia, Vancouver, Canada
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44
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Wang L, Meng X, Zhao Z, Xu D, Fedida D, Wang Z, Huang C. A Novel Cardiac Nav1.5 Channel Mutation, L812Q, Leads to Brugada Syndrome. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.725] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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45
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Murray CI, Maurice Y, Eldstrom J, Fedida D. State-Dependent Crosslinking in IKS Demonstrates a Closed-State Interaction between KCNE1 at F57 and KCNQ1 that Inhibits Channel Opening. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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46
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Wu Y, Dou Y, Fedida D. Role of Charged Residues in the Regulation of Voltage Sensor Movement in Herg K+ Channels. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.4094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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47
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Peters C, Fedida D, Accili E. Allosteric Coupling of the Inner Activation Gate to the Outer Pore of a Potassium Channel. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.2994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Abstract
We recently reported gating currents recorded from hERG channels expressed in mammalian TSA cells and assessed the kinetics at different voltages. We detected 2 distinct components of charge movement with the bulk of the charge being carried by a slower component. Here we compare our findings in TSA cells with recordings made from oocytes using the Cut Open Vaseline Gap clamp (COVG) and go on to directly compare activation of gating charge and ionic currents at 0 and +60 mV. The data show that gating charge saturates and moves more rapidly than ionic current activates suggesting a transition downstream from the movement of the bulk of gating charge is rate limiting for channel opening.
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Affiliation(s)
- Samuel J Goodchild
- Department of Anesthesiology, Pharmacology and Therapeutics; University of British Columbia; Vancouver, BC Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics; University of British Columbia; Vancouver, BC Canada
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Dou Y, Goodchild SJ, Velde RV, Wu Y, Fedida D. The neutral, hydrophobic isoleucine at position I521 in the extracellular S4 domain of hERG contributes to channel gating equilibrium. Am J Physiol Cell Physiol 2013; 305:C468-78. [PMID: 23761630 DOI: 10.1152/ajpcell.00147.2013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [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: 11/22/2022]
Abstract
The human ether-a-go-go related (hERG) potassium channel has unusual functional characteristics in that the rates of channel activation and deactivation are much slower than inactivation, which is attributed to specific structural elements within the NH2 terminus and the S1-S4 voltage-sensing domains (VSD). Although the charged residues in the VSD have been extensively modified and mutated as a result, the role and importance of specific hydrophobic residues in the S4 has been much less explored in studies of hERG gating. We found that charged, but not neutral or hydrophobic, amino acid substitution of isoleucine 521 at the outer end of the S4 transmembrane domain resulted in channels activating at much more negative voltages associated with a marked hyperpolarization of the conductance-voltage (G-V) relationship. The contributions of different physicochemical properties to this effect were probed by chemical modification of channels substituted with cysteine at position I521. When positively charged reagents including tetramethyl-rhodamine-5-maleimide (TMRM), 1-(2-maleimidylethyl)-4-[5-(4-methoxyphenyl)oxazol-2-yl] pyridinium methane-sulfonate (PyMPO), [2-(trimethylammonium)ethyl] methanethiosulfonate chloride (MTSET), and 2-aminoethyl methanethiosulfonate hydrobromide (MTSEA) were bound to the cysteine, I521C channels activated at more negative membrane potentials. To examine the contributions to hERG gating of other residues at the outer end of S4 (520-528), we performed a cysteine scan combined with MTSET modification. Only L520C, along with I521C, shows a substantial hyperpolarizing shift of the G-V relationship upon MTSET modification. The data indicate that the neutral, hydrophobic residue I521 at the extracellular end of S4 is critical for stabilizing the closed conformation of the hERG channel relative to the open state and by comparison with Shaker supports the alignment of hERG I521 with Shaker L361.
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Affiliation(s)
- Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
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50
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Steele DF, Fedida D. Cytoskeletal roles in cardiac ion channel expression. Biochim Biophys Acta 2013; 1838:665-73. [PMID: 23680626 DOI: 10.1016/j.bbamem.2013.05.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 05/01/2013] [Accepted: 05/06/2013] [Indexed: 11/25/2022]
Abstract
The cytoskeleton and cardiac ion channel expression are closely linked. From the time that newly synthesized channels exit the endoplasmic reticulum, they are either traveling along the microtubule or actin cytoskeletons or likely anchored in the plasma membrane or in internal vesicular pools by those scaffolds. Molecular motors, small GTPases and even the dynamics of the cytoskeletons themselves influence the trafficking and expression of the channels. In some cases, the functioning of the channels themselves has profound influences on the cytoskeleton. Here we provide an overview of the current state of knowledge on the involvement of the actin and microtubule cytoskeletons in the trafficking, targeting and expression of cardiac ion channels and a few channels expressed elsewhere. We highlight, also, some of the many questions that remain about these processes. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
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Affiliation(s)
- David F Steele
- Dept. of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - David Fedida
- Dept. of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.
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