scholarly journals Regulation of K+ Conductance by a Hydrogen Bond in Kv2.1, Kv2.2, and Kv1.2 Channels

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 190
Author(s):  
Yuchen Zhang ◽  
Xuefeng Zhang ◽  
Cuiyun Liu ◽  
Changlong Hu
Keyword(s):  
Hydrogen Bond ◽  
Patch Clamp ◽  
Complete Loss ◽  
Slow Inactivation ◽  
Patch Clamp Recording ◽  
Voltage Gated ◽  
Kv Channels ◽  
Shaker Channels ◽  
Cellular Excitability ◽  
Shaker Potassium Channels

The slow inactivation of voltage-gated potassium (Kv) channels plays an important role in controlling cellular excitability. Recently, the two hydrogen bonds (H-bonds) formed by W434-D447 and T439-Y445 have been reported to control the slow inactivation in Shaker potassium channels. The four residues are highly conserved among Kv channels. Our objective was to find the roles of the two H-bonds in controlling the slow inactivation of mammalian Kv2.1, Kv2.2, and Kv1.2 channels by point mutation and patch-clamp recording studies. We found that mutations of the residues equivalent to W434 and T439 in Shaker did not change the slow inactivation of the Kv2.1, Kv2.2, and Kv1.2 channels. Surprisingly, breaking of the inter-subunit H-bond formed by W366 and Y376 (Kv2.1 numbering) by various mutations resulted in the complete loss of K+ conductance of the three Kv channels. In conclusion, we found differences in the H-bonds controlling the slow inactivation of the mammalian Kv channels and Shaker channels. Our data provided the first evidence, to our knowledge, that the inter-subunit H-bond formed by W366 and Y376 plays an important role in regulating the K+ conductance of mammalian Kv2.1, Kv2.2, and Kv1.2 channels.

scholarly journals Probing the Cavity of the Slow Inactivated Conformation of Shaker Potassium Channels

2007 ◽  
Vol 129 (5) ◽  
pp. 403-418 ◽  
Author(s):  
Gyorgy Panyi ◽  
Carol Deutsch
Keyword(s):  
Potassium Channels ◽  
Binding Site ◽  
Conformational Change ◽  
Marked Decrease ◽  
Selectivity Filter ◽  
Slow Inactivation ◽  
Voltage Gated ◽  
Activation Gate ◽  
Shaker Potassium Channels

Slow inactivation involves a local rearrangement of the outer mouth of voltage-gated potassium channels, but nothing is known regarding rearrangements in the cavity between the activation gate and the selectivity filter. We now report that the cavity undergoes a conformational change in the slow-inactivated state. This change is manifest as altered accessibility of residues facing the aqueous cavity and as a marked decrease in the affinity of tetraethylammonium for its internal binding site. These findings have implications for global alterations of the channel during slow inactivation and putative coupling between activation and slow-inactivation gates.

scholarly journals Activation of Piezo1 but not NaV1.2 Channels by Ultrasound at 43 MHz

2017 ◽  
Author(s):  
Martin Loynaz Prieto ◽  
Kamyar Firouzi ◽  
Butrus T. Khuri-Yakub ◽  
Merritt Maduke
Keyword(s):  
Patch Clamp ◽  
Neural Activity ◽  
Continuous Wave ◽  
Molecular Level ◽  
Acoustic Streaming ◽  
Experimental System ◽  
Membrane Stress ◽  
Excitable Cells ◽  
Patch Clamp Recording ◽  
Voltage Gated

ABSTRACTUltrasound (US) can modulate the electrical activity of the excitable tissues but the mechanisms underlying this effect are not understood at the molecular level or in terms of the physical modality through which US exerts its effects. Here we report an experimental system that allows for stable patch-clamp recording in the presence of US at 43 MHz, a frequency known to stimulate neural activity. We describe the effects of US on two ion channels proposed to be involved in the response of excitable cells to US: the mechanosensitive Piezo1 channel and the voltage-gated sodium channel NaV1.2. Our patch-clamp recordings, together with finite-element simulations of acoustic field parameters indicate that Piezo1 channels are activated by continuous wave US at 43 MHz and 50 or 90 W/cm2 through cell membrane stress caused by acoustic streaming. NaV1.2 channels were not affected through this mechanism at these intensities, but their kinetics could be accelerated by US-induced heating.

Dipeptidyl peptidase (DP) 6 and DP10: novel brain proteins implicated in human health and disease

2009 ◽  
Vol 47 (3) ◽  
Author(s):  
Kym McNicholas ◽  
Tong Chen ◽  
Catherine A. Abbott
Keyword(s):  
Human Health ◽  
Splice Variants ◽  
Dipeptidyl Peptidase ◽  
Fibroblast Activation Protein ◽  
Voltage Gated ◽  
Kv Channels ◽  
Cellular Excitability ◽  
Kv4 Channels ◽  
Health And Disease ◽  
Critical Components

AbstractDipeptidyl peptidase (DP) 6 and DP10 are non-enzyme members of the dipeptidyl peptidase IV family, which includes fibroblast activation protein, DP8, and DP9. DP6 and DP10 proteins have been shown to be critical components of voltage-gated potassium (Kv) channels important in determining cellular excitability. The aim of this paper was to review the research to date on DP6 and DP10 structure, expression, and functions. To date, the protein region responsible for modulating Kv4 channels has not been conclusively identified and the significance of the splice variants has not been resolved. Resolution of these issues will improve our overall knowledge of DP6 and DP10 and lead to a better understanding of their role in diseases, such as asthma and Alzheimer's disease.Clin Chem Lab Med 2009;47:262–7.

scholarly journals CatSper and Two-Pore channels (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

2019 ◽  
Vol 2019 (4) ◽  
Author(s):  
Jean-Ju Chung ◽  
David E. Clapham ◽  
David L. Garbers ◽  
Dejian Ren
Keyword(s):  
Plasma Membrane ◽  
Patch Clamp ◽  
Calcium Channels ◽  
Na Channel ◽  
The Novel ◽  
Patch Clamp Recording ◽  
Whole Cell ◽  
Sperm Tail ◽  
Voltage Gated

CatSper channels (CatSper1-4, nomenclature as agreed by NC-IUPHAR [13]) are putative 6TM, voltage-gated, alkalinization-activated calcium permeant channels that are presumed to assemble as a tetramer of α-like subunits and mediate the current ICatSper [21]. In mammals, CatSper subunits are structurally most closely related to individual domains of voltage-activated calcium channels (Cav) [36]. CatSper1 [36], CatSper2 [33] and CatSpers 3 and 4 [25, 19, 32], in common with a putative 2TM auxiliary CatSperβ protein [24] and two putative 1TM associated CatSperγ and CatSperδ proteins [42, 11], are restricted to the testis and localised to the principle piece of sperm tail. The novel cross-species CatSper channel inhibitor, RU1968, has been proposed as a useful tool to aid characterisation of native CatSper channels [37].Two-pore channels (TPCs) are structurally related to CatSpers, CaVs and NaVs. TPCs have a 2x6TM structure with twice the number of TMs of CatSpers and half that of CaVs. There are three animal TPCs (TPC1-TPC3). Humans have TPC1 and TPC2, but not TPC3. TPC1 and TPC2 are localized in endosomes and lysosomes [4]. TPC3 is also found on the plasma membrane and forms a voltage-activated, non-inactivating Na+ channel [5]. All the three TPCs are Na+-selective under whole-cell or whole-organelle patch clamp recording [44, 7, 6]. The channels may also conduct Ca2+ [29].

Differential contributions of voltage-gated potassium channel subunits in enhancing temporal coding in the bushy cells of the ventral cochlear nucleus

2021 ◽  
Author(s):  
Mingyu Fu ◽  
Lu Zhang ◽  
Xiao Xie ◽  
Ningqian Wang ◽  
Zhongju Xiao
Keyword(s):  
Cochlear Nucleus ◽  
Spike Timing ◽  
Temporal Coding ◽  
Membrane Properties ◽  
Membrane Excitability ◽  
Patch Clamp Recording ◽  
Voltage Gated ◽  
Ventral Cochlear Nucleus ◽  
Kv Channels ◽  
Bushy Cells

Temporal coding precision of bushy cells in the ventral cochlear nucleus (VCN), critical for sound localization and communication, depends on the generation of rapid and temporally precise action potentials (APs). Voltage-gated potassium (Kv) channels are critically involved in this. The bushy cells in rat VCN express Kv1.1, 1.2, 1.3, 1.6, 3.1, 4.2 and 4.3 subunits. The Kv1.1 subunit contributes to the generation of a temporally precise single AP. However, the understanding of the functions of other Kv subunits expressed in the bushy cells is limited. Here, we investigated the functional diversity of Kv subunits concerning their contributions to temporal coding. We characterized the electrophysiological properties of the Kv channels with different subunits using whole-cell patch-clamp recording and pharmacological methods. The neuronal firing pattern changed from single to multiple APs only when the Kv1.1 subunit was blocked. The Kv subunits, including the Kv1.1, 1.2, 1.6 or 3.1, were involved in enhancing temporal coding by lowering membrane excitability, shortening AP latencies, reducing jitter and regulating AP kinetics. Meanwhile, all the Kv subunits contributed to rapid repolarization and sharpening peaks by narrowing half-width and accelerating fall rate, while the Kv1.1 subunit also affected the depolarization of AP. The Kv1.1, 1.2 and 1.6 subunits endowed bushy cells with a rapid time constant and a low input resistance of membrane for enhancing spike timing precision. The present results indicate that the Kv channels differentially affect intrinsic membrane properties to optimize the generation of rapid and reliable APs for temporal coding.

Abstract 11691: Atorvastatin Reverses Impaired Voltage-gated K + Channels-mediated Coronary Vasodilation By Upregulating PPARγ In Diabetes (Best of Basic Science Abstract)

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Wen Su ◽  
Wei-Ping Li ◽  
Miao Chen ◽  
Hui Chen ◽  
Hong-Wei Li
Keyword(s):  
Patch Clamp ◽  
Protein Expression ◽  
Current Density ◽  
High Glucose ◽  
Diabetic Rats ◽  
Dependent Manner ◽  
Coronary Vasodilation ◽  
Patch Clamp Recording ◽  
Voltage Gated

Aims: Voltage-gated K + (K v ) channels in vascular smooth muscle cells (VSMCs) play an important role in the regulation of coronary microcirculation. Atorvastatin (ATV) has shown some beneficial effects on vascular function, but the effect of ATV on K v channels-mediated coronary vasodilation remains unknown. The present study was designed to investigate the role of ATV in improving K v channels-mediated coronary dilator function in diabetes and the underlying mechanisms. Methods: Isolated VSMCs were incubated in normal or high glucose medium plus a different dose of ATV for 24 h at 37 o C. Patch-clamp recording and molecular biological techniques were used to assess the function and expression of K v channels. Control or type 2 diabetic rats were treated with ATV (50 mg/kg daily) by oral gavage for 10 weeks. Vasodilation of isolated rat coronary arteries was measured using a pressurized myograph. GW9662, the peroxisome proliferator-activated receptor gamma (PPARγ) antagonist, was used to determine whether the mechanism of ATV-improved K v channel function can be explained by upregulation of PPARγ pathway. Results: Patch-clamp analysis revealed that high glucose reduced K v current density by 58.7 ± 4.6%, which was accompanied by a downregulation of K v 1.2 and K v 1.5 expression. Treatment with ATV reversed the inhibitory effect of high glucose on K v current density in a dose-dependent manner (1 μmol/L, 15.0 ± 2.6%; 10 μmol/L, 49.1 ± 3.8%; 100 μmol/L, 69.9 ± 4.8%; P < 0.05). In addition, ATV restored high glucose-induced downregulation of K v channel protein expression, and the difference was significant in both 10 μmol/L and 100 μmol/L groups. For in vivo study, K v channels-mediated coronary vasodilation was decreased in diabetic rats, compared with controls (9.1 ± 1.3 vs. 36.7 ± 1.4%, P < 0.05), whereas this decrease was partly corrected by ATV (25.0 ± 2.8 vs. 9.1 ± 1.3%, P < 0.05). Treatment with ATV prominently increased protein expression of PPARγ both in vitro and in vivo . The effect of ATV in regulating K v channels and K v channels-mediated vasodilation was markedly blunted by GW9662. Conclusions: In conclusion, treatment with ATV activates PPARγ pathway and preserves K v channel activity in VSMCs, thus providing improvement of coronary dilator function in diabetic rats.

scholarly journals Voltage Dependence of Slow Inactivation in Shaker Potassium Channels Results from Changes in Relative K+ and Na+ Permeabilities

2000 ◽  
Vol 115 (2) ◽  
pp. 107-122 ◽  
Author(s):  
John G. Starkus ◽  
Stefan H. Heinemann ◽  
Martin D. Rayner
Keyword(s):  
Potassium Channels ◽  
Outward Current ◽  
Negative Slope ◽  
Voltage Sensitivity ◽  
Slow Inactivation ◽  
Shaker Channels ◽  
Outward Currents ◽  
Voltage Dependent ◽  
Na Ions ◽  
Shaker Potassium Channels

Time constants of slow inactivation were investigated in NH2-terminal deleted Shaker potassium channels using macro-patch recordings from Xenopus oocytes. Slow inactivation is voltage insensitive in physiological solutions or in simple experimental solutions such as K+o//K+i or Na+o//K+i. However, when [Na+]i is increased while [K+]i is reduced, voltage sensitivity appears in the slow inactivation rates at positive potentials. In such solutions, the I-V curves show a region of negative slope conductance between ∼0 and +60 mV, with strongly increased outward current at more positive voltages, yielding an N-shaped curvature. These changes in peak outward currents are associated with marked changes in the dominant slow inactivation time constant from ∼1.5 s at potentials less than approximately +60 mV to ∼30 ms at more than +150 mV. Since slow inactivation in Shaker channels is extremely sensitive to the concentrations and species of permeant ions, more rapid entry into slow inactivated state(s) might indicate decreased K+ permeation and increased Na+ permeation at positive potentials. However, the N-shaped I-V curve becomes fully developed before the onset of significant slow inactivation, indicating that this N-shaped I-V does not arise from permeability changes associated with entry into slow inactivated states. Thus, changes in the relative contributions of K+ and Na+ ions to outward currents could arise either: (a) from depletions of [K+]i sufficient to permit increased Na+ permeation, or (b) from voltage-dependent changes in K+ and Na+ permeabilities. Our results rule out the first of these mechanisms. Furthermore, effects of changing [K+]i and [K+]o on ramp I-V waveforms suggest that applied potential directly affects relative permeation by K+ and Na+ ions. Therefore, we conclude that the voltage sensitivity of slow inactivation rates arises indirectly as a result of voltage-dependent changes in the ion occupancy of these channels, and demonstrate that simple barrier models can predict such voltage-dependent changes in relative permeabilities.

scholarly journals Combination Formulation of Tetrodotoxin and Lidocaine as a Potential Therapy for Severe Arrhythmias

Marine Drugs ◽  
2019 ◽  
Vol 17 (12) ◽  
pp. 685
Author(s):  
Bihong Hong ◽  
Jianlin He ◽  
Qingqing Le ◽  
Kaikai Bai ◽  
Yongqiang Chen ◽  
...  
Keyword(s):  
Mortality Rate ◽  
Patch Clamp ◽  
Ventricular Arrhythmias ◽  
Treatment Options ◽  
Inhibitory Effect ◽  
Patch Clamp Recording ◽  
Dextran 40 ◽  
Voltage Gated ◽  
Freeze Dried ◽  
Combination Formulation

Severe arrhythmias—such as ventricular arrhythmias—can be fatal, but treatment options are limited. The effects of a combined formulation of tetrodotoxin (TTX) and lidocaine (LID) on severe arrhythmias were studied. Patch clamp recording data showed that the combination of LID and TTX had a stronger inhibitory effect on voltage-gated sodium channel 1.5 (Nav1.5) than that of either TTX or LID alone. LID + TTX formulations were prepared with optimal stability containing 1 μg of TTX, 5 mg of LID, 6 mg of mannitol, and 4 mg of dextran-40 and then freeze dried. This formulation significantly delayed the onset and shortened the duration of arrhythmia induced by aconitine in rats. Arrhythmia-originated death was avoided by the combined formulation, with a decrease in the mortality rate from 64% to 0%. The data also suggests that the anti-arrhythmic effect of the combination was greater than that of either TTX or LID alone. This paper offers new approaches to develop effective medications against arrhythmias.

scholarly journals Hydrogen bonds as molecular timers for slow inactivation in voltage-gated potassium channels

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Stephan A Pless ◽  
Jason D Galpin ◽  
Ana P Niciforovic ◽  
Harley T Kurata ◽  
Christopher A Ahern
Keyword(s):  
Amino Acid ◽  
Hydrogen Bonds ◽  
Slow Inactivation ◽  
Potassium Efflux ◽  
Ion Conductance ◽  
Voltage Gated ◽  
Kv Channels ◽  
Synthetic Amino Acid ◽  
Progressive Loss ◽  
Kinetics Of

Voltage-gated potassium (Kv) channels enable potassium efflux and membrane repolarization in excitable tissues. Many Kv channels undergo a progressive loss of ion conductance in the presence of a prolonged voltage stimulus, termed slow inactivation, but the atomic determinants that regulate the kinetics of this process remain obscure. Using a combination of synthetic amino acid analogs and concatenated channel subunits we establish two H-bonds near the extracellular surface of the channel that endow Kv channels with a mechanism to time the entry into slow inactivation: an intra-subunit H-bond between Asp447 and Trp434 and an inter-subunit H-bond connecting Tyr445 to Thr439. Breaking of either interaction triggers slow inactivation by means of a local disruption in the selectivity filter, while severing the Tyr445–Thr439 H-bond is likely to communicate this conformational change to the adjacent subunit(s).

scholarly journals Serotherapy against Voltage-Gated Sodium Channel-Targeting αToxins from Androctonus Scorpion Venom

Toxins ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 63 ◽  
Author(s):  
Marie-France Martin-Eauclaire ◽  
Sonia Adi-Bessalem ◽  
Djelila Hammoudi-Triki ◽  
Fatima Laraba-Djebari ◽  
Pierre E Bougis
Keyword(s):  
North Africa ◽  
Scorpion Venom ◽  
Fast Inactivation ◽  
Affinity Ligands ◽  
Voltage Gated ◽  
Kv Channels ◽  
Cellular Excitability ◽  
Nav Channels ◽  
Scorpion Stings ◽  
Almost All

Because of their venom lethality towards mammals, scorpions of the Androctonus genus are considered a critical threat to human health in North Africa. Several decades of exploration have led to a comprehensive inventory of their venom components at chemical, pharmacological, and immunological levels. Typically, these venoms contain selective and high affinity ligands for the voltage-gated sodium (Nav) and potassium (Kv) channels that dictate cellular excitability. In the well-studied Androctonus australis and Androctonus mauretanicus venoms, almost all the lethality in mammals is due to the so-called α-toxins. These peptides commonly delay the fast inactivation process of Nav channels, which leads to increased sodium entry and a subsequent cell membrane depolarization. Markedly, their neutralization by specific antisera has been shown to completely inhibit the venom’s lethal activity, because they are not only the most abundant venom peptide but also the most fatal. However, the structural and antigenic polymorphisms in the α-toxin family pose challenges to the design of efficient serotherapies. In this review, we discuss past and present accomplishments to improve serotherapy against Androctonus scorpion stings.

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