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Proceedings of the National Academy of... Oct 2020The opening and closing of voltage-gated ion channels are regulated by voltage sensors coupled to a gate that controls the ion flux across the cellular membrane....
The opening and closing of voltage-gated ion channels are regulated by voltage sensors coupled to a gate that controls the ion flux across the cellular membrane. Modulation of any part of gating constitutes an entry point for pharmacologically regulating channel function. Here, we report on the discovery of a large family of warfarin-like compounds that open the two voltage-gated type 1 potassium (K1) channels K1.5 and Shaker, but not the related K2-, K4-, or K7-type channels. These negatively charged compounds bind in the open state to positively charged arginines and lysines between the intracellular ends of the voltage-sensor domains and the pore domain. This mechanism of action resembles that of endogenous channel-opening lipids and opens up an avenue for the development of ion-channel modulators.
Topics: Animals; High-Throughput Screening Assays; Ion Channel Gating; Kv1.5 Potassium Channel; Molecular Docking Simulation; Patch-Clamp Techniques; Shaker Superfamily of Potassium Channels; Xenopus laevis
PubMed: 33051293
DOI: 10.1073/pnas.2007965117 -
Biochemistry. Biokhimiia Dec 2015Potassium (K+) channels are a widespread superfamily of integral membrane proteins that mediate selective transport of K+ ions through the cell membrane. They have been... (Review)
Review
Potassium (K+) channels are a widespread superfamily of integral membrane proteins that mediate selective transport of K+ ions through the cell membrane. They have been found in all living organisms from bacteria to higher multicellular animals, including humans. Not surprisingly, K+ channels bind ligands of different nature, such as metal ions, low molecular mass compounds, venom-derived peptides, and antibodies. Functionally these substances can be K+ channel pore blockers or modulators. Representatives of the first group occlude the channel pore, like a cork in a bottle, while the second group of ligands alters the operation of channels without physically blocking the ion current. A rich source of K+ channel ligands is venom of different animals: snakes, sea anemones, cone snails, bees, spiders, and scorpions. More than a half of the known K+ channel ligands of polypeptide nature are scorpion toxins (KTx), all of which are pore blockers. These compounds have become an indispensable molecular tool for the study of K+ channel structure and function. A recent special interest is the possibility of toxin application as drugs to treat diseases involving K+ channels or related to their dysfunction (channelopathies).
Topics: Amino Acid Sequence; Animals; Humans; Models, Molecular; Molecular Sequence Data; Potassium Channel Blockers; Potassium Channels; Protein Conformation; Scorpions; Toxins, Biological
PubMed: 26878580
DOI: 10.1134/S0006297915130118 -
Cardiac Electrophysiology Clinics Jun 2016The cardiac action potential is generated by intricate flows of ions across myocyte cell membranes in a coordinated fashion to control myocardial contraction and the... (Review)
Review
The cardiac action potential is generated by intricate flows of ions across myocyte cell membranes in a coordinated fashion to control myocardial contraction and the heart rhythm. Modulation of the flow of these ions in response to a variety of stimuli results in changes to the action potential. Abnormal or altered ion currents can result in cardiac arrhythmias. Abnormalities of autonomic regulation of potassium current play a role in the genesis of cardiac arrhythmias, and alterations in acetylcholine-activated potassium channels may play a key role in atrial fibrillation. Ischemia is another important modulator of cardiac cellular electrophysiology.
Topics: Animals; Arrhythmias, Cardiac; Autonomic Nervous System; Cardiac Electrophysiology; Dogs; Heart; Humans; Mice; Myocardial Ischemia; Potassium Channels
PubMed: 27261826
DOI: 10.1016/j.ccep.2016.01.007 -
The Journal of Biological Chemistry Dec 2017Voltage-activated human ether-á-go-go-related gene (hERG) potassium channels are critical for the repolarization of cardiac action potentials and tune-spike frequency...
Voltage-activated human ether-á-go-go-related gene (hERG) potassium channels are critical for the repolarization of cardiac action potentials and tune-spike frequency adaptation in neurons. Two isoforms of mammalian ERG1 channel subunits, ERG1a and ERG1b, are the principal subunits that conduct the I current in the heart and are also broadly expressed in the nervous system. However, there is little direct evidence that ERG1a and ERG1b form heteromeric channels. Here, using electrophysiology, biochemistry, and fluorescence approaches, we systematically tested for direct interactions between hERG1a and hERG1b subunits. We report 1) that hERG1a dominant-negative subunits suppress hERG1b currents (and vice versa), 2) that disulfide bonds form between single cysteine residues experimentally introduced into an extracellular loop of hERG1a and hERG1b subunits and produce hERG1a-hERG1b dimers, and 3) that hERG1a and hERG1b subunits tagged with fluorescent proteins that are FRET pairs exhibit robust energy transfer at the plasma membrane. Thus, multiple lines of evidence indicated a physical interaction between hERG1a and hERG1b, consistent with them forming heteromeric channels. Moreover, co-expression of variable ratios of and RNA yielded channels with deactivation kinetics that reached a plateau and were different from those of hERG1b channels, consistent with a preference of hERG1b subunits for hERG1a subunits. Cross-linking studies revealed that an equal input of hERG1a and hERG1b yields more hERG1a-hERG1a or hERG1a-hERG1b dimers than hERG1b-hERG1b dimers, also suggesting that hERG1b preferentially interacts with hERG1a. We conclude that hERG1b preferentially forms heteromeric ion channels with hERG1a at the plasma membrane.
Topics: ERG1 Potassium Channel; Ether-A-Go-Go Potassium Channels; Fluorescence Resonance Energy Transfer; Heart; Humans; Ion Channel Gating; Long QT Syndrome; Myocardium; Potassium Channels, Voltage-Gated; Protein Isoforms; Protein Subunits
PubMed: 29089383
DOI: 10.1074/jbc.M117.816488 -
The Journal of General Physiology Oct 2016Ion channels are membrane proteins that mediate efficient ion transport across the hydrophobic core of cell membranes, an unlikely process in their absence. K(+)... (Review)
Review
Ion channels are membrane proteins that mediate efficient ion transport across the hydrophobic core of cell membranes, an unlikely process in their absence. K(+) channels discriminate K(+) over cations with similar radii with extraordinary selectivity and display a wide diversity of ion transport rates, covering differences of two orders of magnitude in unitary conductance. The pore domains of large- and small-conductance K(+) channels share a general architectural design comprising a conserved narrow selectivity filter, which forms intimate interactions with permeant ions, flanked by two wider vestibules toward the internal and external openings. In large-conductance K(+) channels, the inner vestibule is wide, whereas in small-conductance channels it is narrow. Here we raise the idea that the physical dimensions of the hydrophobic internal vestibule limit ion transport in K(+) channels, accounting for their diversity in unitary conductance.
Topics: Ion Transport; Models, Molecular; Potassium; Potassium Channels; Protein Conformation
PubMed: 27619418
DOI: 10.1085/jgp.201611625 -
Journal of the American Chemical Society Jul 2022Inspired by mechanosensitive potassium channels found in nature, we developed a fluorinated amphiphilic cyclophane composed of fluorinated rigid aromatic units connected...
Inspired by mechanosensitive potassium channels found in nature, we developed a fluorinated amphiphilic cyclophane composed of fluorinated rigid aromatic units connected via flexible hydrophilic octa(ethylene glycol) chains. Microscopic and emission spectroscopic studies revealed that the cyclophane could be incorporated into the hydrophobic layer of the lipid bilayer membranes and self-assembled to form a supramolecular transmembrane ion channel. Current recording measurements using cyclophane-containing planer lipid bilayer membranes successfully demonstrated an efficient transmembrane ion transport. We also demonstrated that the ion transport property was sensitive to the mechanical forces applied to the membranes. In addition, ion transport assays using pH-sensitive fluorescence dye revealed that the supramolecular channel possesses potassium ion selectivity. We also performed all-atom hybrid quantum-mechanical/molecular mechanical simulations to assess the channel structures at atomic resolution and the mechanism of selective potassium ion transport. This research demonstrated the first example of a synthetic mechanosensitive potassium channel, which would open a new door to sensing and manipulating biologically important processes and purification of key materials in industries.
Topics: Hydrophobic and Hydrophilic Interactions; Ion Channels; Lipid Bilayers; Potassium; Potassium Channels
PubMed: 35727684
DOI: 10.1021/jacs.2c04118 -
Cardiology 2023The coronavirus disease 2019 (COVID-19) pandemic has led to millions of confirmed cases and deaths worldwide and has no approved therapy. Currently, more than 700 drugs...
Hydroxychloroquine Attenuates hERG Channel by Promoting the Membrane Channel Degradation: Computational Simulation and Experimental Evidence for QT-Interval Prolongation with Hydroxychloroquine Treatment.
INTRODUCTION
The coronavirus disease 2019 (COVID-19) pandemic has led to millions of confirmed cases and deaths worldwide and has no approved therapy. Currently, more than 700 drugs are tested in the COVID-19 clinical trials, and full evaluation of their cardiotoxicity risks is in high demand.
METHODS
We mainly focused on hydroxychloroquine (HCQ), one of the most concerned drugs for COVID-19 therapy, and investigated the effects and underlying mechanisms of HCQ on hERG channel via molecular docking simulations. We further applied the HEK293 cell line stably expressing hERG-wild-type channel (hERG-HEK) and HEK293 cells transiently expressing hERG-p.Y652A or hERG-p.F656A mutants to validate our predictions. Western blot analysis was used to determine the hERG channel, and the whole-cell patch clamp was utilized to record hERG current (IhERG).
RESULTS
HCQ reduced the mature hERG protein in a time- and concentration-dependent manner. Correspondingly, chronic and acute treatment of HCQ decreased the hERG current. Treatment with brefeldin A (BFA) and HCQ combination reduced hERG protein to a greater extent than BFA alone. Moreover, disruption of the typical hERG binding site (hERG-p.Y652A or hERG-p.F656A) rescued HCQ-mediated hERG protein and IhERG reduction.
CONCLUSION
HCQ can reduce the mature hERG channel expression and IhERG via enhancing channel degradation. The QT prolongation effect of HCQ is mediated by typical hERG binding sites involving residues Tyr652 and Phe656.
Topics: Humans; COVID-19; COVID-19 Drug Treatment; ERG1 Potassium Channel; Ether-A-Go-Go Potassium Channels; HEK293 Cells; Hydroxychloroquine; Ion Channels; Molecular Docking Simulation; Mutation
PubMed: 37231805
DOI: 10.1159/000531132 -
Scientific Reports May 2021Voltage-gated potassium (Kv) channels are a family of membrane proteins that facilitate K ion diffusion across the plasma membrane, regulating both resting and action...
Voltage-gated potassium (Kv) channels are a family of membrane proteins that facilitate K ion diffusion across the plasma membrane, regulating both resting and action potentials. Kv channels comprise four pore-forming α subunits, each with a voltage sensing domain, and they are regulated by interaction with β subunits such as those belonging to the KCNE family. Here we conducted a comprehensive biophysical characterization of stoichiometry and protein diffusion across the plasma membrane of the epithelial KCNQ1-KCNE2 complex, combining total internal reflection fluorescence (TIRF) microscopy and a series of complementary Fluorescence Fluctuation Spectroscopy (FFS) techniques. Using this approach, we found that KCNQ1-KCNE2 has a predominant 4:4 stoichiometry, while non-bound KCNE2 subunits are mostly present as dimers in the plasma membrane. At the same time, we identified unique spatio-temporal diffusion modalities and nano-environment organization for each channel subunit. These findings improve our understanding of KCNQ1-KCNE2 channel function and suggest strategies for elucidating the subunit stoichiometry and forces directing localization and diffusion of ion channel complexes in general.
Topics: Action Potentials; Animals; CHO Cells; Cricetulus; Humans; Ion Channel Gating; Models, Molecular; Molecular Conformation; Patch-Clamp Techniques; Potassium Channels; Protein Binding; Protein Interaction Domains and Motifs; Spectrum Analysis; Structure-Activity Relationship
PubMed: 34021177
DOI: 10.1038/s41598-021-90002-2 -
Channels (Austin, Tex.) 2015
Topics: Drug Discovery; Humans; Potassium Channel Blockers; Potassium Channels; Sodium Channel Blockers; Voltage-Gated Sodium Channels
PubMed: 26646476
DOI: 10.1080/19336950.2015.1077650 -
Journal of Applied Physiology... May 2020Exercise training is known to prolong the ventricular cardiomyocyte action potential duration (APD), increasing Ca influx and contractility. The prolonged APD is caused,...
Exercise training is known to prolong the ventricular cardiomyocyte action potential duration (APD), increasing Ca influx and contractility. The prolonged APD is caused, in part, by a decreased responsiveness to β-adrenergic agonists. The study's aims were to elucidate the mechanisms by which exercise training alters β-adrenergic regulation and to determine the involvement of delayed rectifier potassium channels ( and ) in the response. Rats were randomly assigned to wheel running-trained (TRN) or sedentary (SED) groups. After 6-8 wk of training, myocytes were isolated from the apex and base regions of the left ventricle, and current-voltage relationships of and were measured. Myocytes from SED and TRN rats exhibit lower current compared with , and a regional difference in was observed, with higher current in apex compared with base myocytes. Wheel running decreased at positive voltages and reduced responsiveness to β-agonist. channel subunit KCNQ1 content was higher in apex compared with base, and exercise training decreased KCNQ1 and KCNE1 subunit content in both regions. Exercise training had no effect on β-adrenergic receptor content but reduced the kinase anchoring protein yotiao and β-adrenergic receptor kinase GRK2 compared with SED rats. The reduced KCNQ1, KCNE1, and yotiao provide a mechanism underlying the training-induced decrease in current, while downregulation of GRK2 would reduce inactivation of the β-AR, maintaining adrenergic stimulation of contractility. Collectively, these membrane protein changes in response to TRN provide a mechanism for prolonging the APD, increasing myocyte efficiency in low stress conditions, while increasing contractility. Results demonstrate that exercise training (TRN) downregulates ventricular channel current and the channel's responsiveness to β-agonist factors mediated by TRN-induced decline in channel subunits KCNQ1 and KCNE1 and the A-kinase anchoring protein yotiao. The reduced current helps explain the TRN-induced prolongation of the action potential in basal conditions and, coupled with previously reported upregulation of the K channel, results in a more efficient heart that is better able to respond to beat-by-beat changes in metabolism.
Topics: A Kinase Anchor Proteins; Action Potentials; Adrenergic Agents; Animals; Cytoskeletal Proteins; KCNQ1 Potassium Channel; Motor Activity; Myocytes, Cardiac; Physical Conditioning, Animal; Potassium Channels, Voltage-Gated; Rats
PubMed: 32240024
DOI: 10.1152/japplphysiol.00802.2019