Search Results (149)

Hypoxic pulmonary vasoconstriction (HPV) optimizes gas exchange but, when impaired, can result in life-threatening hypoxemia. Moreover, under conditions of generalized alveolar hypoxia, HPV can result in pulmonary hypertension. Voltage-gated K⁺ channels (K_v channels) are key to HPV: a change in the intracellular hydrogen peroxide (H₂O₂) levels during acute hypoxia is assumed to modulate these channels’ activity to trigger HPV. However, there are longstanding conflicting findings on whether H₂O₂ inhibits or activates K_v channels. Therefore, we hypothesized that H₂O₂ affects K_v channels depending on the experimental conditions, i.e., the H₂O₂ concentration, the channel’s subunit configuration or the experimental clamping potential in electrophysiological recordings. Therefore, cRNAs encoding the K_v1.5 channel and the auxiliary K_vβ subunits (K_vβ1.1, K_vβ1.4) were generated via in vitro transcription before being injected into Xenopus laevis oocytes for heterologous expression. The K⁺ currents of homomeric (Kv1.5) or heteromeric (K_v1.5/K_vβ1.1 or K_v1.5/K_vβ1.4) channels were assessed by two-electrode voltage clamp. The response of the K_v channels to H₂O₂ was markedly dependent on (a) the clamping potential, (b) the H₂O₂ concentration, and (c) the K_v channel’s subunit composition. In conclusion, our data highlight the importance of the choice of experimental conditions when assessing the H₂O₂ sensitivity of K_v channels in the context of HPV, thus providing an explanation for the long-lasting controversial findings reported in the literature. Full article

Voltage-gated potassium channels Kv7.1, encoded by the gene KCNQ1, play critical roles in various physiological processes. In cardiomyocytes, the complex Kv7.1-KCNE1 mediates the slow component of the delayed rectifier potassium current that is essential for the action potential repolarization. Over 1000 KCNQ1 missense variants, many of which are associated with long QT syndrome, are reported in ClinVar and other databases. However, over 600 variants are of uncertain clinical significance (VUS), have conflicting interpretations of pathogenicity, or lack germline information. Computational prediction of the damaging potential of such variants is important for the diagnostics and treatment of cardiac disease. Here, we collected 1750 benign and pathogenic missense variants of Kv channels from databases ClinVar, Humsavar, and Ensembl Variation and tested 26 bioinformatics tools in their ability to identify known pathogenic or likely pathogenic (P/LP) variants. The best-performing tool, AlphaMissense, predicted the pathogenicity of 195 VUSs in Kv7.1. Among these, 79 variants of 66 wildtype residues (WTRs) are also reported as P/LP variants in sequentially matching positions of at least one hKv7.1 paralogue. In available cryoEM structures of Kv7.1 with activated and deactivated voltage-sensing domains, 52 WTRs form intersegmental contacts with WTRs of ClinVar-listed variants, including 21 WTRs with P/LP variants. ClinPred and paralogue annotation methods consistently predicted that 21 WTRs of KCNE1 have 34 VUSs with damaging potential. Among these, 8 WTRs are contacting 23 Kv7.1 WTRs with 13 ClinVar-listed variants in the AlphaFold3 model. Analysis of intersegmental contacts in CryoEM and AlphaFold3 structures suggests atomic mechanisms of dysfunction for some VUSs. Full article

This paper investigates 6.5 kV SiC trench gate p-channel IGBTs using Sentaurus TCAD simulations. The proposed superjunction structure is compared to conventional designs to highlight its advantages. The p-IGBT, fabricated on an n-type substrate, offers notable commercial advantages over n-IGBTs on p-type substrates. The n-shield can effectively protect the trench gate oxide in the corners of SiC. The n-shield and n-pillar can be either floating or grounded, with the floating shield condition significantly enhancing injection and improving forward conduction performance. The superjunction floating shield p-IGBT (SJFS-p-IGBT) improves forward conduction voltage (V_F) by 47% and 15% compared to conventional planar gate p-IGBT (CP-p-IGBT) and grounded shield p-IGBT (CGS-p-IGBT), respectively. For switching characteristics, the superjunction grounded shield p-IGBT (SJGS-p-IGBT) improves turn-off time (t_off) by 15% compared to the conventional floating shield p-IGBT (CFS-p-IGBT). The trade-off between V_F and turn-off energy (E_off) is analyzed, showing that the SJFS-p-IGBT offers a better trade-off. A negative temperature coefficient is observed at high buffer layer doping concentration and elevated temperatures, leading to an increase in V_F. This provides design guidance for devices operating in parallel at high temperatures. These results demonstrate the SJ’s potential to enhance efficiency and performance for ultra-high voltage applications. Full article

Background: The development of cerebral organoids created from human pluripotent stem cells in 3D culture may greatly improve the discovery of neuropsychiatric medicines. Methods: In the current study we differentiated neural organoids from a human pluripotent stem cell line in vitro, recorded the development of neurophysiological activity using multielectrode arrays (MEAs) and characterized the neuropharmacology of synaptic signaling over 8 months in vitro. In addition, we investigated the ability of these organoids to display epileptiform activity in response to a convulsant agent and the effects of antiseizure medicines to inhibit this abnormal activity. Results: Single and bursts of action potentials from individual neurons and network bursts were recorded on the MEA plates and significantly increased and became more complex from week 7 to week 30, consistent with neural network formation. Neural spiking was reduced by the Na channel blocker tetrodotoxin but increased by the inhibitor of K_V7 potassium channels XE991, confirming the involvement of voltage-gated sodium and potassium channels in action potential activity. The GABA antagonists bicuculline and picrotoxin each increased the spike rate, consistent with inhibitory synaptic signaling. In contrast, the glutamate receptor antagonist kynurenic acid inhibited the spike rate, consistent with excitatory synaptic transmission in the organoids. The convulsant 4-aminopyridine increased spiking, bursts and synchronized firing, consistent with epileptiform activity in vitro. The anticonvulsants carbamazepine, ethosuximide and diazepam each inhibited this epileptiform neural activity. Conclusions: Together, our data demonstrate that neural organoids form inhibitory and excitatory synaptic circuits, generate epileptiform activity in response to a convulsant agent and detect the antiseizure properties of diverse antiepileptic drugs, supporting their value in drug discovery. Full article

Neuropathic pain is a chronic and debilitating disorder of the somatosensory system that affects a significant proportion of the population and is characterized by abnormal responses such as hyperalgesia and allodynia. Voltage-gated ion channels, including sodium (Na_V), calcium (Ca_V), and potassium (K_V) channels, play a pivotal role in modulating neuronal excitability and pain signal transmission following nerve injury. This review intends to provide a comprehensive analysis of the molecular and cellular mechanisms by which dysregulation in the expression, localization, and function of specific Na_V channel subtypes (mainly Na_V1.7 and Na_V1.8) and their auxiliary subunits contributes to aberrant neuronal activation, the generation of ectopic discharges, and sensitization in neuropathic pain. Likewise, special emphasis is placed on the crucial role of Ca_V channels, particularly Ca_V2.2 and the auxiliary subunit Ca_Vα₂δ, whose overexpression increases calcium influx, neurotransmitter release, and neuronal hyperexcitability, thus maintaining persistent pain states. Furthermore, K_V channels (particularly K_V7 channels) function as brakes on neuronal excitability, and their dysregulation facilitates the development and maintenance of neuropathic pain. Therefore, targeting specific K_V channel subtypes to restore their function is also a promising therapeutic strategy for alleviating neuropathic pain symptoms. On the other hand, recent advances in the development of small molecules as selective modulators or inhibitors targeting voltage-gated ion channels are also discussed. These agents have improved efficacy and safety profiles in preclinical and clinical studies by attenuating pathophysiological channel activity and restoring neuronal function. This review seeks to contribute to guiding future research and drug development toward more effective mechanism-based treatments by discussing the molecular mechanisms underlying neuropathic pain and highlighting translational therapeutic opportunities. Full article

The conopeptide αD-FrXXA was previously isolated by our team from the venom of the vermivorous snail Conus fergusoni. This toxin is composed of two chains of 47 amino acids and inhibits neuronal and muscular subtypes of nAChR. In this study, we explored its effects on voltage-gated potassium channels heterologously expressed in Xenopus laevis oocytes using the two-electrode voltage-clamp technique (TEVC). At a concentration of 15 μM, αD-FrXXA was able to inhibit by 50% or more the currents of four subtypes of the Kv1 subfamily and slightly inhibit (<20%) two subtypes of the EAG subfamily. The conopeptide αD-FrXXA inhibits in a concentration-dependent manner the subtypes Kv1.3 (IC₅₀ 0.38 ± 0.06 μM) and Kv1.6 (IC₅₀ 0.52 ± 0.14 μM). The results reported here are noteworthy because this α-conopeptide behaves similarly to the α/κJ-PlXIVA conopeptide that inhibits nAChR and Kv channels. Full article

Voltage-gated potassium (Kv) channels are e ssential for shaping action potentials and rely on anionic lipids for proper gating, yet the mechanistic basis of lipid–channel interactions remains unclear. Cryo-electron microscopy studies suggest that, in the down state, arginine residues of the voltage sensor draw lipid phosphates upward, leading to a local membrane thinning of ~5 Å—an effect absent in the open state. To test whether membrane thickness directly affects voltage sensor function, we reconstituted Kv channels from Aeropyrum pernix (KvAP) into planar lipid bilayers containing photoswitchable lipids. Upon blue light illumination, the membrane thickened, and KvAP activity increased; UV light reversed both effects. Our findings indicate that membrane thickening weakens the interaction between lipid phosphates and voltage-sensing arginines in the down state, lowering the energy barrier for the transition to the up state and thereby promoting channel opening. This non-genetic, membrane-mediated approach provides a new strategy to control ion channel activity using light and establishes a direct, reversible link between membrane mechanics and voltage sensing, with potential applications in the remote control of neuronal excitability. Full article

A de novo missense variant in KCNH3 has been identified in a patient with neurological symptoms including seizures. Here, we confirm the previously reported loss-of-function features for the associated Kv12.2 mutant A371V and investigate the underlying mechanism. Loss of function was not rescued by low temperature during channel biogenesis. Elevated external K⁺ reduced the rectification of Kv12.2 conductance as predicted by the GHK current equation, allowing the detection of currents mediated by homomeric A371V Kv12.2 channels and a detailed biophysical analysis of the mutant. Compared to wild-type, the voltage dependences of activation and deactivation of A371V Kv12.2 channels were shifted in the positive direction by 15 to 20 mV. Moreover, A371V Kv12.2 channels exhibited accelerated inactivation kinetics combined with a dramatic negative shift in the voltage dependence of inactivation by more than 100 mV. Even in heteromeric wild-type + A371V Kv12.2 channels, inactivation was enhanced, leading to a significant current reduction at physiological potentials. Our Kv12.2 data show similarities to Kv11 channels regarding C-type inactivation and differences regarding the sensitivity to external K⁺ and pharmacological inhibition of inactivation. The gating modification caused by the A371V amino acid substitution in Kv12.2 renders loss of function voltage-dependent, with a possible impact on neuronal excitability and firing behavior. Full article

Background/Objectives: Kv2 channels have important conducting and nonconducting functions and are regulated by their co-assembly with ‘silent’ Kv subunits, including Kv9.1. Kv9.1 is co-expressed with Kv2 channels in sensory neurons, and a common allele that changes Ile489 to Val in human Kv9.1 is associated with pain hypersensitivity in patients. The mechanism responsible for this association remains unknown, but we hypothesise that these two variants differ in their regulation of Kv2.1 properties, and this is what we set out to test. Methods: Expression was carried out using HEK293 cells, OHeLa cells, and primary cultures of hippocampal neurons, and the biophysical and trafficking properties of homomeric and heteromeric channels were assessed by confocal fluorescence microscopy and patch clamp analysis. Results: Both Kv9.1Ile and Kv9.1Val were retained within the endoplasmic reticulum when expressed individually, but when co-expressed with Kv2.1, they co-localised with Kv2.1 within the surface clusters. Both variants reduced the surface expression of Kv2.1 channels and the size of channel clusters, with Kv9.1Val producing a greater reduction in surface expression in both the HeLa cells and neurons. They both caused a similar hyperpolarising shift in the voltage dependence of channel activation and inactivation. Concatamers of Kv2.1 and Kv9.1 suggested that both 3:1 and 2:2 ratios of Kv2.1 to Kv9.1 were permitted, although 2:2 resulted in lower surface expression and function. Conclusions: The Ile489Val substitution in Kv9.1 does not disrupt its ability to co-assemble with Kv2 channels, nor its effects on the voltage-dependence of channel gating, but it did produce a greater reduction in the Kv2.1 surface expression, suggesting that this underlies its association with pain hypersensitivity. Full article

Electrical stimulation of the skin has proven effective in pain management and antibacterial treatment, particularly in wound healing and counteracting the aging processes. The latter processes rely on epidermal cell migration, increased fibroblast proliferation, and upregulation of extracellular matrix protein expression. While an electrical field stimulates these processes, it is unclear how the electrical signal results in transcriptional control. Here, we postulate that the activation of voltage-gated channels, specifically voltage-gated potassium channels Kv1.3, is implicated in initiating the downstream signaling pathways that lead to increased collagen expression. We postulate that Kv1.3 and possibly calcium-activated potassium channel activity leads to the engagement of store-operated calcium channels and modulates the intracellular calcium ions distribution. In turn, changes in intracellular calcium concentration can activate calcium-generated transcriptional effectors. The Kv1.3 channel, identified via fluorescence imaging with ShK toxin (peptide), shows high-level expression in the human dermal fibroblast cell membrane. We also performed proliferation, collagen expression, and calcium imaging studies for variable electrical fields to help understand the link between the electrical stimulation, Kv1.3 channels, intracellular calcium concentration, and protein expression. Full article

Breast cancer remains the leading cause of cancer-related mortality among women worldwide, with limited therapeutic efficacy due to treatment resistance and adverse effects. Emerging evidence suggests that ion channels play crucial roles in tumor progression, regulating proliferation, apoptosis, migration, and metastasis. Voltage-gated potassium (Kv) and sodium (Nav) channels have been implicated in oncogenic signaling pathways. Scorpion venom peptides, known for their selective ion-channel-blocking properties, have demonstrated promising antineoplastic activity. This study explores the potential therapeutic applications of bioactive fractions derived from Chihuahuanus coahuilae, in breast cancer cell lines. Through chromatographic separation, mass spectrometry, and functional assays, we assess their effects on cell viability, proliferation, and ion channel modulation. Our preliminary data suggest that these venom-derived peptides interfere with cancer cell homeostasis by altering ion fluxes, promoting apoptosis, and inhibiting metastatic traits. These findings support the therapeutic potential of ion-channel-targeting peptides as selective anticancer agents. Further investigations into their molecular mechanisms may pave the way for novel, targeted therapies with improved efficacy and specificity for breast cancer treatment. Full article

Scorpion venom peptides, particularly those derived from Asian species, have garnered significant attention, offering therapeutic potential in pain management, cancer, anticoagulation, and infectious diseases. This review provides a comprehensive analysis of scorpion venom peptides, focusing on their roles as voltage-gated sodium (Nav), potassium (Kv), and calcium (Cav) channel modulators. It analyzed Nav1.7 inhibition for analgesia, Kv1.3 blockade for anticancer activity, and membrane disruption for antimicrobial effects. While the low targeting specificity and high toxicity of some scorpion venom peptides pose challenges to their clinical application, recent research has made strides in overcoming these limitations. This review summarizes the latest progress in scorpion venom peptide research, discussing their mechanisms of action, therapeutic potential, and challenges in clinical translation. This work aims to provide new insights and directions for the development of novel therapeutic drugs. Full article

The core subunits of the K_V7.2, K_V7.3, and K_V7.5 channels, encoded by the KCNQ2, KCNQ3, and KCNQ5 genes, are expressed across various cell types and play a key role in generating the M-type K⁺ current (I_K(M)). This current is characterized by an activation threshold at low voltages and displays slow activation and deactivation kinetics. Variations in the amplitude and gating kinetics of I_K(M) can significantly influence membrane excitability. Notably, I_K(M) demonstrates distinct voltage-dependent hysteresis when subjected to prolonged isosceles-triangular ramp pulses. In this review, we explore various small-molecule modulators that can either inhibit or enhance the amplitude of I_K(M), along with their perturbations on its gating kinetics and voltage-dependent hysteresis. The inhibitors of I_K(M) highlighted here include bisoprolol, brivaracetam, cannabidiol, nalbuphine, phenobarbital, and remdesivir. Conversely, compounds such as flupirtine, kynurenic acid, naringenin, QO-58, and solifenacin have been shown to enhance I_K(M). These modulators show potential as pharmacological or therapeutic strategies for treating certain disorders linked to gain-of-function or loss-of-function mutations in M-type K⁺ (K_V7x or KCNQx) channels. Full article

Multidrug-resistant tuberculosis (MDR-TB) patients are treated with a standardised, short World Health Organization (WHO) regimen which includes clofazimine (CFZ) and bedaquiline (BDQ) antibiotics. These two antibiotics lead to the development of QT prolongation in patients, inhibiting potassium (K⁺) uptake by targeting the voltage-gated K⁺ (Kv)11.1 (hERG) channel of the cardiomyocytes (CMs). However, the involvement of these antibiotics to regulate other K⁺ transporters of the CMs, as potential mechanisms of QT prolongation, has not been explored. This study determined the effects of CFZ and BDQ on sodium, potassium–adenosine triphosphatase (Na⁺,K⁺-ATPase) activity of CMs using rat cardiomyocytes (RCMs). These cells were treated with varying concentrations of CFZ and BDQ individually and in combination (1.25–5 mg/L). Thereafter, Na⁺,K⁺-ATPase activity was determined, followed by intracellular adenosine triphosphate (ATP) quantification and cellular viability determination. Furthermore, molecular docking of antibiotics with Na⁺,K⁺-ATPase was determined. Both antibiotics demonstrated dose–response inhibition of Na⁺,K⁺-ATPase activity of the RCMs. The greatest inhibition was demonstrated by combinations of CFZ and BDQ, followed by BDQ alone and, lastly, CFZ. Neither antibiotic, either individually or in combination, demonstrated cytotoxicity. Molecular docking revealed an interaction of both antibiotics with Na⁺,K⁺-ATPase, with BDQ showing higher protein-binding affinity than CFZ. The inhibitory effects of CFZ and BDQ, individually and in combination, on the activity of Na⁺,K⁺-ATPase pump of the RCMs highlight the existence of additional mechanisms of QT prolongation by these antibiotics. Full article

Pathogenic variants in KCNC3, which encodes the voltage-gated potassium channel Kv3.3, are associated with spinocerebellar ataxia type 13. SCA13 is a neurodegenerative disease characterized by ataxia, dysarthria and oculomotor dysfunction, often in combination with other signs and symptoms such as cognitive impairment. Known disease-causing variants are localized in the protein coding regions and predominantly in the transmembrane and voltage sensing domains. In a patient with an ataxic movement disorder and progressive cognitive decline, the c.-6C>A variant was detected in the Kozak sequence of KCNC3. The Kozak sequence is responsible for efficient initiation of translation. Functional analysis of the new c.-6C>A variant and the upstream 5’-UTR region of KCNC3 by luciferase assays, quantitative PCR and methylation analysis shows increased protein expression but no effect on transcription rate. Therefore, increased translation initiation of KCNC3 transcripts compared to wild-type Kozak sequence seems to be the cause of the increased expression. Variants in the regulatory elements of disease-causing genes probably play an underestimated role. Full article