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The Journal of Biological Chemistry Aug 2022Biological membranes are composed of a wide variety of lipids. Phosphoinositides (PIPns) in the membrane inner leaflet only account for a small percentage of the total...
Biological membranes are composed of a wide variety of lipids. Phosphoinositides (PIPns) in the membrane inner leaflet only account for a small percentage of the total membrane lipids but modulate the functions of various membrane proteins, including ion channels, which play important roles in cell signaling. KcsA, a prototypical K channel that is small, simple, and easy to handle, has been broadly examined regarding its crystallography, in silico molecular analysis, and electrophysiology. It has been reported that KcsA activity is regulated by membrane phospholipids, such as phosphatidylglycerol. However, there has been no quantitative analysis of the correlation between direct lipid binding and the functional modification of KcsA, and it is unknown whether PIPns modulate KcsA function. Here, using contact bubble bilayer recording, we observed that the open probability of KcsA increased significantly (from about 10% to 90%) when the membrane inner leaflet contained only a small percentage of PIPns. In addition, we found an increase in the electrophysiological activity of KcsA correlated with a larger number of negative charges on PIPns. We further analyzed the affinity of the direct interaction between PIPns and KcsA using microscale thermophoresis and observed a strong correlation between direct lipid binding and the functional modification of KcsA. In conclusion, our approach was able to reconstruct the direct modification of KcsA by PIPns, and we propose that it can also be applied to elucidate the mechanism of modification of other ion channels by PIPns.
Topics: Bacterial Proteins; Membrane Lipids; Phosphatidylinositols; Phospholipids; Potassium Channels
PubMed: 35839854
DOI: 10.1016/j.jbc.2022.102257 -
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 -
Advances in Experimental Medicine and... 2023Ca/voltage-gated, large conductance K channels (BK) are formed by homotetrameric association of α (slo1) subunits. Their activity, however, is suited to tissue-specific...
Ca/voltage-gated, large conductance K channels (BK) are formed by homotetrameric association of α (slo1) subunits. Their activity, however, is suited to tissue-specific physiology largely due to their association with regulatory subunits (β and γ types), chaperone proteins, localized signaling, and the channel's lipid microenvironment. PIP and cholesterol can modulate BK activity independently of downstream signaling, yet activating Ca levels and regulatory subunits control ligand action. At physiological Ca and voltages, cholesterol and PIP reduce and increase slo1 channel activity, respectively. Moreover, slo1 proteins provide sites that seem to recognize cholesterol and PIP: seven CRAC motifs in the slo1 cytosolic tail and a string of positively charged residues (Arg, Lys, Lys) immediately after S6, respectively. A model that could explain the modulation of BK activity by cholesterol and/or PIP is hypothesized. The roles of additional sites, whether in slo1 or BK regulatory subunits, for PIP and/or cholesterol to modulate BK function are also discussed.
Topics: Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Cytosol; Ion Channel Gating; Signal Transduction; Cholesterol; Large-Conductance Calcium-Activated Potassium Channels
PubMed: 36988883
DOI: 10.1007/978-3-031-21547-6_8 -
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 -
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 -
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 -
Cells Oct 2021Two-pore-domain potassium (K-) channels conduct outward K currents that maintain the resting membrane potential and modulate action potential repolarization. Members of... (Review)
Review
Two-pore-domain potassium (K-) channels conduct outward K currents that maintain the resting membrane potential and modulate action potential repolarization. Members of the K channel family are widely expressed among different human cell types and organs where they were shown to regulate important physiological processes. Their functional activity is controlled by a broad variety of different stimuli, like pH level, temperature, and mechanical stress but also by the presence of lipids or pharmacological agents. In patients suffering from cardiovascular diseases, alterations in K-channel expression and function have been observed, suggesting functional significance and a potential therapeutic role of these ion channels. For example, upregulation of atrial specific K3.1 (TASK-1) currents in atrial fibrillation (AF) patients was shown to contribute to atrial action potential duration shortening, a key feature of AF-associated atrial electrical remodelling. Therefore, targeting K3.1 (TASK-1) channels might constitute an intriguing strategy for AF treatment. Further, mechanoactive K2.1 (TREK-1) currents have been implicated in the development of cardiac hypertrophy, cardiac fibrosis and heart failure. Cardiovascular expression of other K channels has been described, functional evidence in cardiac tissue however remains sparse. In the present review, expression, function, and regulation of cardiovascular K channels are summarized and compared among different species. Remodelling patterns, observed in disease models are discussed and compared to findings from clinical patients to assess the therapeutic potential of K channels.
Topics: Animals; Atrial Remodeling; Cardiovascular Diseases; Gene Expression Regulation; Humans; Myocardium; Potassium Channels, Tandem Pore Domain
PubMed: 34831137
DOI: 10.3390/cells10112914 -
European Journal of Medicinal Chemistry Nov 2023Voltage-gated potassium channel K1.3 inhibitors have been shown to be effective in preventing T-cell proliferation and activation by affecting intracellular Ca...
Voltage-gated potassium channel K1.3 inhibitors have been shown to be effective in preventing T-cell proliferation and activation by affecting intracellular Ca homeostasis. Here, we present the structure-activity relationship, K1.3 inhibition, and immunosuppressive effects of new thiophene-based K1.3 inhibitors with nanomolar potency on K current in T-lymphocytes and K1.3 inhibition on Ltk cells. The new K1.3 inhibitor trans-18 inhibited K1.3 -mediated current in phytohemagglutinin (PHA)-activated T-lymphocytes with an IC value of 26.1 nM and in mammalian Ltk cells with an IC value of 230 nM. The K1.3 inhibitor trans-18 also had nanomolar potency against K1.3 in Xenopus laevis oocytes (IC = 136 nM). The novel thiophene-based K1.3 inhibitors impaired intracellular Ca signaling as well as T-cell activation, proliferation, and colony formation.
Topics: Animals; Mammals; Potassium Channel Blockers; Potassium Channels; Potassium Channels, Voltage-Gated; Structure-Activity Relationship; T-Lymphocytes; Thiophenes; Immunosuppressive Agents
PubMed: 37454520
DOI: 10.1016/j.ejmech.2023.115561