scholarly journals The insecticide deltamethrin enhances sodium channel slow inactivation of human Nav1.9, Nav1.8 and Nav1.7

2021 ◽  
pp. 115676
Author(s):  
Stefanie Nicole Bothe ◽  
Angelika Lampert
Keyword(s):  
Sodium Channel ◽  
Slow Inactivation

P1597Two novel mutations in SCN5A gene cause enhanced inactivation and lead to Brugada syndrome

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
A Zaytseva ◽  
A V Karpushev ◽  
A V Karpushev ◽  
Y Fomicheva ◽  
Y Fomicheva ◽  
...  
Keyword(s):  
Steady State ◽  
Sodium Channel ◽  
Brugada Syndrome ◽  
Slow Inactivation ◽  
Fast Inactivation ◽  
Novel Mutations ◽  
Patch Clamp Technique ◽  
Inactivation Curve ◽  
Voltage Gated ◽  
Cardiac Sodium Channel

Abstract Background Mutations in gene SCN5A, encoding cardiac potential-dependent sodium channel Nav1.5, are associated with various arrhythmogenic disorders among which the Brugada syndrome (BrS) and the Long QT syndrome (LQT) are the best characterized. BrS1 is associated with sodium channel dysfunction, which can be reflected by decreased current, impaired activation and enhanced inactivation. We found two novel mutations in our patients with BrS and explored their effect on fast and slow inactivation of cardiac sodium channel. Purpose The aim of this study was to investigate the effect of BrS (Y739D, L1582P) mutations on different inactivation processes in in vitro model. Methods Y739D and L1582P substitutions were introduced in SCN5A cDNA using site-directed mutagenesis. Sodium currents were recorded at room temperature in transfected HEK293-T cells using patch-clamp technique with holding potential −100 mV. In order to access the fast steady-state inactivation curve we used double-pulse protocol with 10 ms prepulses. To analyze voltage-dependence of slow inactivation we used two-pulse protocol with 10s prepulse, 20ms test pulse and 25ms interpulse at −100mV to allow recovery from fast inactivation. Electrophysiological measurements are presented as mean ±SEM. Results Y739D mutation affects highly conserved tyrosine 739 among voltage-gated sodium and calcium channels in the segment IIS2. Mutation L1582P located in the loop IVS4-S5, and leucine in this position is not conserved among voltage-gated channels superfamily. We have shown that Y739D leads to significant changes in both fast and slow inactivation, whereas L1582P enhanced slow inactivation only. Steady-state fast inactivation for Y739D was shifted on 8.9 mV towards more negative potentials compare with that for WT, while L1582P did not enhanced fast inactivation (V1/2 WT: −62.8±1.7 mV; Y739D: −71.7±2.3 mV; L1582P: −58.7±1.4 mV). Slow inactivation was increased for both substitutions (INa (+20mV)/INa (−100mV) WT: 0.45±0.03; Y739D: 0,34±0.09: L1582P: 0.38±0.04). Steady-state fast inactivation Conclusions Both mutations, observed in patients with Brugada syndrome, influence on the slow inactivation process. Enhanced fast inactivation was shown only for Y739D mutant. The more dramatic alterations in sodium channel biophysical characteristics are likely linked with mutated residue conservativity. Acknowledgement/Funding RSF #17-15-01292

scholarly journals A gating charge interaction required for late slow inactivation of the bacterial sodium channel NavAb

2013 ◽  
Vol 142 (3) ◽  
pp. 181-190 ◽  
Author(s):  
Tamer M. Gamal El-Din ◽  
Gilbert Q. Martinez ◽  
Jian Payandeh ◽  
Todd Scheuer ◽  
William A. Catterall
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Late Phase ◽  
Membrane Potentials ◽  
Charge Movement ◽  
Slow Inactivation ◽  
Functional Studies ◽  
Voltage Gated Sodium Channels ◽  
Gating Charge ◽  
Charge Interaction

Voltage-gated sodium channels undergo slow inactivation during repetitive depolarizations, which controls the frequency and duration of bursts of action potentials and prevents excitotoxic cell death. Although homotetrameric bacterial sodium channels lack the intracellular linker-connecting homologous domains III and IV that causes fast inactivation of eukaryotic sodium channels, they retain the molecular mechanism for slow inactivation. Here, we examine the functional properties and slow inactivation of the bacterial sodium channel NavAb expressed in insect cells under conditions used for structural studies. NavAb activates at very negative membrane potentials (V1/2 of approximately −98 mV), and it has both an early phase of slow inactivation that arises during single depolarizations and reverses rapidly, and a late use-dependent phase of slow inactivation that reverses very slowly. Mutation of Asn49 to Lys in the S2 segment in the extracellular negative cluster of the voltage sensor shifts the activation curve ∼75 mV to more positive potentials and abolishes the late phase of slow inactivation. The gating charge R3 interacts with Asn49 in the crystal structure of NavAb, and mutation of this residue to Cys causes a similar positive shift in the voltage dependence of activation and block of the late phase of slow inactivation as mutation N49K. Prolonged depolarizations that induce slow inactivation also cause hysteresis of gating charge movement, which results in a requirement for very negative membrane potentials to return gating charges to their resting state. Unexpectedly, the mutation N49K does not alter hysteresis of gating charge movement, even though it prevents the late phase of slow inactivation. Our results reveal an important molecular interaction between R3 in S4 and Asn49 in S2 that is crucial for voltage-dependent activation and for late slow inactivation of NavAb, and they introduce a NavAb mutant that enables detailed functional studies in parallel with structural analysis.

scholarly journals Mutagenesis Studies Investigating Slow Inactivation of Sodium Channel Nav1.6

2013 ◽  
Vol 104 (2) ◽  
pp. 134a-135a
Author(s):  
Angelika Lampert ◽  
Andrias O'Reilly ◽  
Esther Eberhardt
Keyword(s):  
Sodium Channel ◽  
Slow Inactivation

Frequency- and voltage-dependent effects of disopyramide in canine Purkinje fibers

1989 ◽  
Vol 67 (7) ◽  
pp. 710-721 ◽  
Author(s):  
Matthew A. Flemming ◽  
Betty I. Sasyniuk
Keyword(s):  
Potassium Channels ◽  
Action Potential ◽  
Sodium Channel ◽  
Action Potential Duration ◽  
Refractory Period ◽  
Drug Effect ◽  
Effective Refractory Period ◽  
Slow Inactivation ◽  
Purkinje Fibers ◽  
Rate Dependent

The voltage- and frequency-dependent blocking actions of disopyramide were assessed in canine Purkinje fibers within the framework of concentrations, membrane potentials, and heart rates which have relevance to the therapeutic actions of this drug. [Formula: see text] was used to assess the magnitude of sodium channel block. Disopyramide produced a concentration- and rate-dependent increase in the magnitude and kinetics of [Formula: see text] depression. Effects on activation time (used as an estimate of drug effect on conduction) were exactly analogous to effects on [Formula: see text]. A concentration-dependent increase in tonic block was also observed. Despite significant increases in tonic block at more depolarized potentials, rate-dependent block increased only marginally with membrane potential over the range of potentials in which propagated action potentials occur. Increases in extracellular potassium concentration accentuated drug effect on [Formula: see text] but attenuated drug effect on action potential duration. Recovery from rate-dependent block followed two exponential processes with time constants of 689 ± 535 ms and 15.7 ± 2.7 s. The latter component represents dissociation of drug from its binding site and the former probably represents recovery from slow inactivation. A concentration-dependent increase in the amplitude of the first component suggested that disopyramide may promote slow inactivation. There was less than 5% recovery from block during intervals equivalent to clinical diastole. Thus, depression of beats of all degrees of prematurity was similar to that of basic drive beats. Prolongation of action potential duration by therapeutic concentrations of drug following a long quiescent interval was minimal. However, profound lengthening of action potential duration occurred following washout of drug effect at a time when [Formula: see text] depression had reverted to normal, suggesting that binding of disopyramide to potassium channels may not be readily reversed. Variable effects on action potential duration may thus be attributed to a block of the window current flowing during the action potential being partially or over balanced by block of potassium channels. Purkinje fiber refractoriness was prolonged in a frequency-dependent manner. Disopyramide did not significantly alter the effective refractory period of basic beats but did increase the effective refractory period of sequential tightly coupled extra stimuli. The results can account for the antiarrhythmic actions of disopyramide during a rapid tachycardia and prevention of its initiation by programmed electrical stimulation.Key words: action potential duration, effective refractory period, upstroke velocity, conduction, rate of sodium channel unblocking.

scholarly journals Interaction between Fast and Ultra-slow Inactivation in the Voltage-gated Sodium Channel

2002 ◽  
Vol 277 (40) ◽  
pp. 37105-37115 ◽  
Author(s):  
Karlheinz Hilber ◽  
Walter Sandtner ◽  
Oliver Kudlacek ◽  
Blanca Schreiner ◽  
Ian Glaaser ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Slow Inactivation ◽  
Voltage Gated Sodium Channel ◽  
Voltage Gated

scholarly journals Identification of the Benzyloxyphenyl Pharmacophore: A Structural Unit That Promotes Sodium Channel Slow Inactivation

2012 ◽  
Vol 3 (12) ◽  
pp. 1037-1049 ◽  
Author(s):  
Amber M. King ◽  
Xiao-Fang Yang ◽  
Yuying Wang ◽  
Erik T. Dustrude ◽  
Cindy Barbosa ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Structural Unit ◽  
Slow Inactivation

scholarly journals GS-967 and Eleclazine Block Sodium Channels in Human Induced Pluripotent Stem Cell-derived Cardiomyocytes

2020 ◽  
Author(s):  
Franck Potet ◽  
Defne E. Egecioglu ◽  
Paul W. Burridge ◽  
Alfred L. George
Keyword(s):  
Stem Cell ◽  
Sodium Channel ◽  
Sodium Channels ◽  
Pluripotent Stem Cell ◽  
Sodium Current ◽  
Induced Pluripotent Stem Cell ◽  
Slow Inactivation ◽  
Molecular Pharmacology ◽  
Recovery From Inactivation ◽  
Induced Pluripotent

ABSTRACTGS-967 and eleclazine (GS-6615) are novel sodium channel inhibitors exhibiting antiarrhythmic effects in various in vitro and in vivo models. The antiarrhythmic mechanism has been attributed to preferential suppression of late sodium current (INaL). Here, we took advantage of a throughput automated electrophysiology platform (SyncroPatch 768PE) to investigate the molecular pharmacology of GS-967 and eleclazine on peak sodium current (INaP) recorded from human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes. We compared GS-967 and eleclazine to the antiarrhythmic drug lidocaine, the prototype INaL inhibitor ranolazine, and the slow inactivation enhancing drug lacosamide. In human induced pluripotent stem cell-derived cardiomyocytes, GS-967 and eleclazine caused a reduction of INaP in a frequency-dependent manner consistent with use-dependent block (UDB). GS-967 and eleclazine had similar efficacy but evoked more potent UDB of INaP (IC50=0.07 and 0.6 μM, respectively) than ranolazine (7.8 μM), lidocaine (133.5 μM) and lacosamide (158.5 μM). In addition, GS-967 and eleclazine exerted more potent effects on slow inactivation and recovery from inactivation compared to the other sodium channel blocking drugs we tested. The greater UDB potency of GS-967 and eleclazine was attributed to the significantly higher association rates (KON) and moderate unbinding rate (KOFF) of these two compounds with sodium channels. We propose that substantial UDB contributes to the observed antiarrhythmic efficacy of GS-967 and eleclazine.SIGNIFICANCE STATEMENTWe investigated the molecular pharmacology of GS-967 and eleclazine on sodium channels in human induced pluripotent stem cell derived cardiomyocytes using a high throughput automated electrophysiology platform. Sodium channel inhibition by GS-967 and eleclazine has unique features including accelerating the onset of slow inactivation and impairing recovery from inactivation. These effects combined with rapid binding and moderate unbinding kinetics explain potent use-dependent block, which we propose contributes to their observed antiarrhythmic efficacy.

scholarly journals Differential effect of lacosamide on Nav1.7 variants from responsive and non-responsive patients with small fibre neuropathy

Brain ◽  
2020 ◽  
Vol 143 (3) ◽  
pp. 771-782 ◽  
Author(s):  
Julie I R Labau ◽  
Mark Estacion ◽  
Brian S Tanaka ◽  
Bianca T A de Greef ◽  
Janneke G J Hoeijmakers ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Dorsal Root ◽  
Voltage Dependence ◽  
Dependent Manner ◽  
Slow Inactivation ◽  
Fast Inactivation ◽  
Small Fibre Neuropathy ◽  
Small Fibre ◽  
Dependent Inhibition ◽  
Hyperpolarizing Shift

Abstract Small fibre neuropathy is a common pain disorder, which in many cases fails to respond to treatment with existing medications. Gain-of-function mutations of voltage-gated sodium channel Nav1.7 underlie dorsal root ganglion neuronal hyperexcitability and pain in a subset of patients with small fibre neuropathy. Recent clinical studies have demonstrated that lacosamide, which blocks sodium channels in a use-dependent manner, attenuates pain in some patients with Nav1.7 mutations; however, only a subgroup of these patients responded to the drug. Here, we used voltage-clamp recordings to evaluate the effects of lacosamide on five Nav1.7 variants from patients who were responsive or non-responsive to treatment. We show that, at the clinically achievable concentration of 30 μM, lacosamide acts as a potent sodium channel inhibitor of Nav1.7 variants carried by responsive patients, via a hyperpolarizing shift of voltage-dependence of both fast and slow inactivation and enhancement of use-dependent inhibition. By contrast, the effects of lacosamide on slow inactivation and use-dependence in Nav1.7 variants from non-responsive patients were less robust. Importantly, we found that lacosamide selectively enhances fast inactivation only in variants from responders. Taken together, these findings begin to unravel biophysical underpinnings that contribute to responsiveness to lacosamide in patients with small fibre neuropathy carrying select Nav1.7 variants.

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