scholarly journals Flow and shortcuts along the Shaker Kv channel slow inactivation gating cycle

2020 ◽  
Vol 152 (8) ◽  
Author(s):  
Valerie Abigail Nirenberg ◽  
Ofer Yifrach
Keyword(s):  
Slow Inactivation ◽  
Kv Channel ◽  
Inactivation Gating

Closing the cycle of Kv channel slow inactivation gating.

scholarly journals Slow Inactivation Does Not Block the Aqueous Accessibility to the Outer Pore of Voltage-gated Na Channels

2002 ◽  
Vol 120 (4) ◽  
pp. 509-516 ◽  
Author(s):  
Arie F. Struyk ◽  
Stephen C. Cannon
Keyword(s):  
Reaction Rates ◽  
Slow Inactivation ◽  
Na Channels ◽  
Fast Inactivation ◽  
Voltage Gated ◽  
State Dependent ◽  
Gating Mechanism ◽  
Dependent Change ◽  
Outer Pore ◽  
Inactivation Gating

Slow inactivation of voltage-gated Na channels is kinetically and structurally distinct from fast inactivation. Whereas structures that participate in fast inactivation are well described and include the cytoplasmic III-IV linker, the nature and location of the slow inactivation gating mechanism remains poorly understood. Several lines of evidence suggest that the pore regions (P-regions) are important contributors to slow inactivation gating. This has led to the proposal that a collapse of the pore impedes Na current during slow inactivation. We sought to determine whether such a slow inactivation-coupled conformational change could be detected in the outer pore. To accomplish this, we used a rapid perfusion technique to measure reaction rates between cysteine-substituted side chains lining the aqueous pore and the charged sulfhydryl-modifying reagent MTS-ET. A pattern of incrementally slower reaction rates was observed at substituted sites at increasing depth in the pore. We found no state-dependent change in modification rates of P-region residues located in all four domains, and thus no change in aqueous accessibility, between slow- and nonslow-inactivated states. In domains I and IV, it was possible to measure modification rates at residues adjacent to the narrow DEKA selectivity filter (Y401C and G1530C), and yet no change was observed in accessibility in either slow- or nonslow-inactivated states. We interpret these results as evidence that the outer mouth of the Na pore remains open while the channel is slow inactivated.

HMJ-53A accelerates slow inactivation gating of voltage-gated K+ channels in mouse neuroblastoma N2A cells

2008 ◽  
Vol 54 (7) ◽  
pp. 1128-1135 ◽  
Author(s):  
Chia-Chia Chao ◽  
Jeffrey Shieh ◽  
Sheng-Chu Kuo ◽  
Bor-Tsang Wu ◽  
Mann-Jen Hour ◽  
...  
Keyword(s):  
Slow Inactivation ◽  
K Channels ◽  
Voltage Gated ◽  
Mouse Neuroblastoma ◽  
N2a Cells ◽  
Inactivation Gating

scholarly journals Molecular Motions of the Outer Ring of Charge of the Sodium Channel

2003 ◽  
Vol 122 (3) ◽  
pp. 323-332 ◽  
Author(s):  
Wei Xiong ◽  
Ronald A. Li ◽  
Yanli Tian ◽  
Gordon F. Tomaselli
Keyword(s):  
Structural Rearrangement ◽  
Outer Ring ◽  
Na Channel ◽  
Slow Inactivation ◽  
Redox Catalyst ◽  
Cysteine Mutagenesis ◽  
Charged Ring ◽  
Outer Pore ◽  
Inactivation Gating

In contrast to fast inactivation, the molecular basis of sodium (Na) channel slow inactivation is poorly understood. It has been suggested that structural rearrangements in the outer pore mediate slow inactivation of Na channels similar to C-type inactivation in potassium (K) channels. We probed the role of the outer ring of charge in inactivation gating by paired cysteine mutagenesis in the rat skeletal muscle Na channel (rNav1.4). The outer charged ring residues were substituted with cysteine, paired with cysteine mutants at other positions in the external pore, and coexpressed with rat brain β1 in Xenopus oocytes. Dithiolthreitol (DTT) markedly increased the current in E403C+E758C double mutant, indicating the spontaneous formation of a disulfide bond and proximity of the α carbons of these residues of no more than 7 Å. The redox catalyst Cu(II) (1,10-phenanthroline)3 (Cu(phe)3) reduced the peak current of double mutants (E403C+E758C, E403C+D1241C, E403C+D1532C, and D1241C+D1532C) at a rate proportional to the stimulation frequency. Voltage protocols that favored occupancy of slow inactivation states completely prevented Cu(phe)3 modification of outer charged ring paired mutants E403C+E758C, E403C+D1241C, and E403C+D1532C. In contrast, voltage protocols that favored slow inactivation did not prevent Cu(phe)3 modification of other double mutants such as E403C+W756C, E403C+W1239C, and E403C+W1531C. Our data suggest that slow inactivation of the Na channel is associated with a structural rearrangement of the outer ring of charge.

scholarly journals A unique mechanism of inactivation gating of the Kv channel family member Kv7.1 and its modulation by PIP2 and calmodulin

2020 ◽  
Vol 6 (51) ◽  
pp. eabd6922
Author(s):  
Maya Lipinsky ◽  
William Sam Tobelaim ◽  
Asher Peretz ◽  
Luba Simhaev ◽  
Adva Yeheskel ◽  
...  
Keyword(s):  
Family Member ◽  
Selectivity Filter ◽  
Wild Type ◽  
Voltage Gated ◽  
Kv Channel ◽  
Kv Channels ◽  
Dependent Inactivation ◽  
Voltage Dependent ◽  
Inactivation Gating ◽  
Unique Mechanism

Inactivation of voltage-gated K+ (Kv) channels mostly occurs by fast N-type or/and slow C-type mechanisms. Here, we characterized a unique mechanism of inactivation gating comprising two inactivation states in a member of the Kv channel superfamily, Kv7.1. Removal of external Ca2+ in wild-type Kv7.1 channels produced a large, voltage-dependent inactivation, which differed from N- or C-type mechanisms. Glu295 and Asp317 located, respectively, in the turret and pore entrance are involved in Ca2+ coordination, allowing Asp317 to form H-bonding with the pore helix Trp304, which stabilizes the selectivity filter and prevents inactivation. Phosphatidylinositol 4,5-bisphosphate (PIP2) and Ca2+-calmodulin prevented Kv7.1 inactivation triggered by Ca2+-free external solutions, where Ser182 at the S2-S3 linker relays the calmodulin signal from its inner boundary to the external pore to allow proper channel conduction. Thus, we revealed a unique mechanism of inactivation gating in Kv7.1, exquisitely controlled by external Ca2+ and allosterically coupled by internal PIP2 and Ca2+-calmodulin.

Low intracellular pH and chemical agents slow inactivation gating in sodium channels of muscle

Nature ◽  
1980 ◽  
Vol 284 (5754) ◽  
pp. 360-363 ◽  
Author(s):  
Wolfgang Nonner ◽  
Bruce C. Spalding ◽  
Bertil Hille
Keyword(s):  
Intracellular Ph ◽  
Sodium Channels ◽  
Slow Inactivation ◽  
Chemical Agents ◽  
Inactivation Gating

scholarly journals Role of peroxisome proliferators-activated receptor-gamma in advanced glycation end product-mediated functional loss of voltage-gated potassium channel in rat coronary arteries

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
W Li ◽  
S.D Gao ◽  
B Hua ◽  
Q.B Liu ◽  
H.R Liu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Coronary Artery ◽  
Coronary Arteries ◽  
Funding Source ◽  
Peroxisome Proliferators ◽  
Advanced Glycation ◽  
Coronary Vasodilation ◽  
Voltage Gated ◽  
Kv Channel ◽  
Ppar Γ

Abstract Background Voltage-gated K+ (Kv) channels in coronary artery smooth muscle cells (CSMCs), especially the major specific Kv1 subfamily, contribute to coronary artery vasodilation. Advanced glycation end products (AGEs) have been strongly implicated in diabetes-related cardiovascular complications. Our previous study showed AGEs can impair Kv channel-mediated coronary vasodilation by reducing Kv channel activity. However, its underlying mechanism remains unclear. Purpose Here, we used isolated rat small coronary arteries (RSCAs) and primary CSMCs to investigate the effect of AGEs on Kv channel-mediated coronary vasodilation and the possible involvement of peroxisome proliferators-activated receptor (PPAR)-γ pathway. Methods RSCAs and primary CSMCs were isolated, cultured and treated with bovine serum albumin (BSA), AGE-BSA, alagrebrium (ALA, AGE cross-linking breaker), pioglitazone (PIO) and/or GW9662, and then divided into the following groups: DMEM, BSA, AGE, AGE+ALA, AGE+PIO, and AGE+PIO+GW9662. Kv channel-mediated coronary vasodilation was analyzed using wire myograph. Histology and immunohistochemistry of RSCAs were performed. Western blot was used to detect the protein expression of RAGE, the major Kv1 channel subunits expressed in CSMCs (Kv1.2/1.5), PPAR-γ, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-2 (NOX-2). Results AGEs markedly reduced forskolin-induced Kv channel-mediated vasodilation of RSCAs by interacting with the receptor for AGEs (RAGE), and ALA or PIO significantly reversed this effect. In both RSCAs and primary CSMCs, AGEs decreased Kv1.2 and Kv1.5 channel protein expression, inhibited PPAR-γ expression, increased RAGE and NOX-2 expression. Treatment with ALA or PIO partially reversed the effects of AGEs on Kv1.2/Kv1.5 expression, accompanied by elevation of PPAR-γ level and diminished oxidative stress. Conclusion AGE/RAGE axis-induced inhibition of PPAR-γ pathway and enhancement of oxidative stress may contribute to AGEs-mediated Kv channel dysfunction and coronary vasodilation in RSCAs. Our results may provide new insights into developing therapeutic strategies to manage diabetic vasculature. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): National Natural Science Foundation of China; Natural Science Foundation of Beijing (7172059)

Inactivation gating and 4-AP sensitivity in human brain Kv1.4 potassium channel

1999 ◽  
Vol 831 (1-2) ◽  
pp. 43-54 ◽  
Author(s):  
Susan I.V Judge ◽  
Mervyn J Monteiro ◽  
Jay Z Yeh ◽  
Christopher T Bever
Keyword(s):  
Human Brain ◽  
Potassium Channel ◽  
Inactivation Gating

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

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