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International Journal of Molecular... Nov 2023Modulation of the human Ether-à-go-go-Related Gene (hERG) channel, a crucial voltage-gated potassium channel in the repolarization of action potentials in ventricular... (Review)
Review
Modulation of the human Ether-à-go-go-Related Gene (hERG) channel, a crucial voltage-gated potassium channel in the repolarization of action potentials in ventricular myocytes of the heart, has significant implications on cardiac electrophysiology and can be either antiarrhythmic or proarrhythmic. For example, hERG channel blockade is a leading cause of long QT syndrome and potentially life-threatening arrhythmias, such as . Conversely, hERG channel blockade is the mechanism of action of Class III antiarrhythmic agents in terminating ventricular tachycardia and fibrillation. In recent years, it has been recognized that less proarrhythmic hERG blockers with clinical potential or Class III antiarrhythmic agents exhibit, in addition to their hERG-blocking activity, a second action that facilitates the voltage-dependent activation of the hERG channel. This facilitation is believed to reduce the proarrhythmic potential by supporting the final repolarizing of action potentials. This review covers the pharmacological characteristics of hERG blockers/facilitators, the molecular mechanisms underlying facilitation, and their clinical significance, as well as unresolved issues and requirements for research in the fields of ion channel pharmacology and drug-induced arrhythmias.
Topics: Humans; Ether-A-Go-Go Potassium Channels; ERG1 Potassium Channel; Potassium Channel Blockers; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Myocytes, Cardiac; Action Potentials
PubMed: 38003453
DOI: 10.3390/ijms242216261 -
Biomedicine & Pharmacotherapy =... Dec 2023Primary and acquired therapy resistance is a major problem in patients with BRAF-mutant melanomas being treated with BRAF and MEK inhibitors (BRAFI, MEKi). Therefore,...
Primary and acquired therapy resistance is a major problem in patients with BRAF-mutant melanomas being treated with BRAF and MEK inhibitors (BRAFI, MEKi). Therefore, development of alternative therapy regimes is still required. In this regard, new drug combinations targeting different pathways to induce apoptosis could offer promising alternative approaches. Here, we investigated the combination of proteasome and Kv1.3 potassium channel inhibition on chemo-resistant, BRAF inhibitor-resistant as well as sensitive human melanoma cells. Our experiments demonstrated that all analyzed melanoma cell lines were sensitive to proteasome inhibitor treatment at concentrations that are not toxic to primary human fibroblasts. To further reduce proteasome inhibitor-associated side effects, and to foster apoptosis, potassium channels, which are other targets to induce pro-apoptotic effects in cancer cells, were blocked. In support, combined exposure of melanoma cells to proteasome and Kv1.3 channel inhibitor resulted in synergistic effects and significantly reduced cell viability. On the molecular level, enhanced apoptosis correlated with an increase of intracellular Kv1.3 channels and pro-apoptotic proteins such as Noxa and Bak and a reduction of anti-apoptotic proteins. Thus, use of combined therapeutic strategies triggering different apoptotic pathways may efficiently prevent the outgrowth of drug-resistant and -sensitive BRAF-mutant melanoma cells. In addition, this could be the basis for an alternative approach to treat other tumors expressing mutated BRAF such as non-small-cell lung cancer.
Topics: Humans; Proteasome Endopeptidase Complex; Kv1.3 Potassium Channel; Proteasome Inhibitors; Proto-Oncogene Proteins B-raf; Carcinoma, Non-Small-Cell Lung; Drug Resistance, Neoplasm; Cell Line, Tumor; Lung Neoplasms; Melanoma; Protein Kinase Inhibitors; Apoptosis Regulatory Proteins; Mutation
PubMed: 37816303
DOI: 10.1016/j.biopha.2023.115635 -
BioRxiv : the Preprint Server For... Aug 20234-aminopyridine (4AP) is a potassium (K) channel blocker used clinically to improve walking in people with multiple sclerosis (MS). 4AP binds to exposed K channels in...
4-aminopyridine (4AP) is a potassium (K) channel blocker used clinically to improve walking in people with multiple sclerosis (MS). 4AP binds to exposed K channels in demyelinated axons, reducing the leakage of intracellular K and enhancing impulse conduction. Multiple derivatives of 4AP capable of blocking K channels have been reported including three radiolabeled with positron emitting isotopes for imaging demyelinated lesions using positron emission tomography (PET). Here, we describe 3-fluoro-5-methylpyridin-4-amine (5Me3F4AP), a novel K channel blocker with potential application in PET. 5Me3F4AP has comparable potency to 4AP and the PET tracer 3-fluoro-4-aminopyridine (3F4AP). Compared to 3F4AP, 5Me3F4AP is more lipophilic (logD = 0.664 ± 0.005 0.414 ± 0.002) and slightly more basic (p = 7.46 ± 0.01 . 7.37 ± 0.07). In addition, 5Me3F4AP appears to be more permeable to an artificial brain membrane and more stable towards oxidation by the cytochrome P450 enzyme family 2 subfamily E member 1 (CYP2E1), responsible for the metabolism of 4AP and 3F4AP. Taken together, 5Me3F4AP has promising properties for PET imaging warranting additional investigation.
PubMed: 37609160
DOI: 10.1101/2023.08.08.550404 -
Molecular Cell Dec 2023Modulation of large conductance intracellular ligand-activated potassium (BK) channel family (Slo1-3) by auxiliary subunits allows diverse physiological functions in...
Modulation of large conductance intracellular ligand-activated potassium (BK) channel family (Slo1-3) by auxiliary subunits allows diverse physiological functions in excitable and non-excitable cells. Cryoelectron microscopy (cryo-EM) structures of voltage-gated potassium (Kv) channel complexes have provided insights into how voltage sensitivity is modulated by auxiliary subunits. However, the modulation mechanisms of BK channels, particularly as ligand-activated ion channels, remain unknown. Slo1 is a Ca-activated and voltage-gated BK channel and is expressed in neurons, muscle cells, and epithelial cells. Using cryo-EM and electrophysiology, we show that the LRRC26-γ1 subunit modulates not only voltage but also Ca sensitivity of Homo sapiens Slo1. LRRC26 stabilizes the active conformation of voltage-senor domains of Slo1 by an extracellularly S4-locking mechanism. Furthermore, it also stabilizes the active conformation of Ca-sensor domains of Slo1 intracellularly, which is functionally equivalent to intracellular Ca in the activation of Slo1. Such a dual allosteric modulatory mechanism may be general in regulating the intracellular ligand-activated BK channel complexes.
Topics: Humans; Calcium; Cryoelectron Microscopy; Ion Channel Gating; Large-Conductance Calcium-Activated Potassium Channels; Ligands; Potassium; Allosteric Regulation
PubMed: 38035882
DOI: 10.1016/j.molcel.2023.11.005 -
Frontiers in Pharmacology 2023The human ether-a-go-go-related gene (hERG) not only encodes a potassium-selective voltage-gated ion channel essential for normal electrical activity in the heart but is...
The human ether-a-go-go-related gene (hERG) not only encodes a potassium-selective voltage-gated ion channel essential for normal electrical activity in the heart but is also a major drug anti-target. Genetic hERG mutations and blockage of the channel pore by drugs can cause long QT syndrome, which predisposes individuals to potentially deadly arrhythmias. However, not all hERG-blocking drugs are proarrhythmic, and their differential affinities to discrete channel conformational states have been suggested to contribute to arrhythmogenicity. We used Rosetta electron density refinement and homology modeling to build structural models of open-state hERG channel wild-type and mutant variants (Y652A, F656A, and Y652A/F656 A) and a closed-state wild-type channel based on cryo-electron microscopy structures of hERG and EAG1 channels. These models were used as protein targets for molecular docking of charged and neutral forms of amiodarone, nifekalant, dofetilide, d/l-sotalol, flecainide, and moxifloxacin. We selected these drugs based on their different arrhythmogenic potentials and abilities to facilitate hERG current. Our docking studies and clustering provided atomistic structural insights into state-dependent drug-channel interactions that play a key role in differentiating safe and harmful hERG blockers and can explain hERG channel facilitation through drug interactions with its open-state hydrophobic pockets.
PubMed: 38035013
DOI: 10.3389/fphar.2023.1244166 -
Frontiers in Molecular Neuroscience 2023Developmental and epileptic encephalopathy (DEE) is a condition characterized by severe seizures and a range of developmental impairments. Pathogenic variants in ,...
BACKGROUND
Developmental and epileptic encephalopathy (DEE) is a condition characterized by severe seizures and a range of developmental impairments. Pathogenic variants in , encoding for potassium channel subunit, cause -related DEE. This study aimed to examine the relationships between genotype and phenotype in -related DEE.
METHODS
In total, 12 patients were enrolled in this study for genetic testing, clinical analysis, and developmental evaluation. Pathogenic variants of KCNQ2 were characterized through a whole-cell electrophysiological recording expressed in Chinese hamster ovary (CHO) cells. The expression levels of the KCNQ2 subunit and its localization at the plasma membrane were determined using Western blot analysis.
RESULTS
Seizures were detected in all patients. All DEE patients showed evidence of developmental delay. In total, 11 KCNQ2 variants were identified, including 10 missense variants from DEE patients and one truncating variant from a patient with self-limited neonatal epilepsy (SeLNE). All variants were found to be loss of function through analysis of M-currents using patch-clamp recordings. The functional impact of variants on M-current in heteromericKCNQ2/3 channels may be associated with the severity of developmental disorders in DEE. The variants with dominant-negative effects in heteromeric channels may be responsible for the profound developmental phenotype.
CONCLUSION
The mechanism underlying -related DEE involves a reduction of the M-current through dominant-negative effects, and the severity of developmental disorders in DEE may be predicted by the impact of variants on the M-current of heteromericKCNQ2/3 channels.
PubMed: 37497102
DOI: 10.3389/fnmol.2023.1205265 -
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 -
Cell Death & Disease Jan 2024MitoK is a channel of the inner mitochondrial membrane that controls mitochondrial K influx according to ATP availability. Recently, the genes encoding the pore-forming...
MitoK is a channel of the inner mitochondrial membrane that controls mitochondrial K influx according to ATP availability. Recently, the genes encoding the pore-forming (MITOK) and the regulatory ATP-sensitive (MITOSUR) subunits of mitoK were identified, allowing the genetic manipulation of the channel. Here, we analyzed the role of mitoK in determining skeletal muscle structure and activity. Mitok muscles were characterized by mitochondrial cristae remodeling and defective oxidative metabolism, with consequent impairment of exercise performance and altered response to damaging muscle contractions. On the other hand, constitutive mitochondrial K influx by MITOK overexpression in the skeletal muscle triggered overt mitochondrial dysfunction and energy default, increased protein polyubiquitination, aberrant autophagy flux, and induction of a stress response program. MITOK overexpressing muscles were therefore severely atrophic. Thus, the proper modulation of mitoK activity is required for the maintenance of skeletal muscle homeostasis and function.
Topics: Adenosine Triphosphate; Potassium Channels; Mitochondria; Muscle, Skeletal; Mitochondria, Heart
PubMed: 38233399
DOI: 10.1038/s41419-024-06426-x -
Circulation Research Mar 2024Vascular large conductance Ca-activated K (BK) channel, composed of the α-subunit (BK-α) and the β1-subunit (BK-β1), is a key determinant of coronary vasorelaxation...
BACKGROUND
Vascular large conductance Ca-activated K (BK) channel, composed of the α-subunit (BK-α) and the β1-subunit (BK-β1), is a key determinant of coronary vasorelaxation and its function is impaired in diabetic vessels. However, our knowledge of diabetic BK channel dysregulation is incomplete. The Sorbs2 (Sorbin homology [SoHo] and Src homology 3 [SH3] domains-containing protein 2), is ubiquitously expressed in arteries, but its role in vascular pathophysiology is unknown.
METHODS
The role of Sorbs2 in regulating vascular BK channel activity was determined using patch-clamp recordings, molecular biological techniques, and in silico analysis.
RESULTS
Sorbs2 is not only a cytoskeletal protein but also an RNA-binding protein that binds to BK channel proteins and BK-α mRNA, regulating BK channel expression and function in coronary smooth muscle cells. Molecular biological studies reveal that the SH3 domain of Sorbs2 is necessary for Sorbs2 interaction with BK-α subunits, while both the SH3 and SoHo domains of Sorbs2 interact with BK-β1 subunits. Deletion of the SH3 or SoHo domains abolishes the Sorbs2 effect on the BK-α/BK-β1 channel current density. Additionally, is a target gene of the Nrf2 (nuclear factor erythroid-2-related factor 2), which binds to the promoter of and regulates Sorbs2 expression in coronary smooth muscle cells. In vivo studies demonstrate that knockout mice at 4 months of age display a significant decrease in BK channel expression and function, accompanied by impaired BK channel Ca-sensitivity and BK channel-mediated vasodilation in coronary arteries, without altering their body weights and blood glucose levels. Importantly, Sorbs2 expression is significantly downregulated in the coronary arteries of db/db type 2 diabetic mice.
CONCLUSIONS
Sorbs2, a downstream target of Nrf2, plays an important role in regulating BK channel expression and function in vascular smooth muscle cells. Vascular Sorbs2 is downregulated in diabetes. Genetic knockout of manifests coronary BK channelopathy and vasculopathy observed in diabetic mice, independent of obesity and glucotoxicity.
Topics: Mice; Animals; Diabetes Mellitus, Experimental; NF-E2-Related Factor 2; Channelopathies; Large-Conductance Calcium-Activated Potassium Channel beta Subunits; Muscle, Smooth, Vascular; Large-Conductance Calcium-Activated Potassium Channels; Coronary Vessels; RNA-Binding Proteins; Adaptor Proteins, Signal Transducing
PubMed: 38362769
DOI: 10.1161/CIRCRESAHA.123.323538 -
Frontiers in Pharmacology 2023Despite improvements in treatment, lung cancer is still a major health problem worldwide. Among lung cancer subtypes, the most frequent is represented by adenocarcinoma... (Review)
Review
Despite improvements in treatment, lung cancer is still a major health problem worldwide. Among lung cancer subtypes, the most frequent is represented by adenocarcinoma (belonging to the Non-Small Cell Lung Cancer class) although the most challenging and harder to treat is represented by Small Cell Lung Cancer, that occurs at lower frequency but has the worst prognosis. For these reasons, the standard of care for these patients is represented by a combination of surgery, radiation therapy and chemotherapy. In this view, searching for novel biomarkers that might help both in diagnosis and therapy is mandatory. In the last 30 years it was demonstrated that different families of ion channels are overexpressed in both lung cancer cell lines and primary tumours. The altered ion channel profile may be advantageous for diagnostic and therapeutic purposes since most of them are localised on the plasma membrane thus their detection is quite easy, as well as their block with specific drugs and antibodies. This review focuses on ion channels (Potassium, Sodium, Calcium, Chloride, Anion and Nicotinic Acetylcholine receptors) in lung cancer (both Non-Small Cell Lung Cancer and Small Cell Lung Cancer) and recapitulate the up-to-date knowledge about their role and clinical relevance for a potential use in the clinical setting, for lung cancer diagnosis and therapy.
PubMed: 37942486
DOI: 10.3389/fphar.2023.1283623