scholarly journals Sodium Channel Inactivation Is Altered by Substitution of Voltage Sensor Positive Charges

1997 ◽  
Vol 110 (4) ◽  
pp. 403-413 ◽  
Author(s):  
Kris J. Kontis ◽  
Alan L. Goldin
Keyword(s):  
Sodium Channel ◽  
Voltage Dependence ◽  
Voltage Sensor ◽  
Voltage Sensitivity ◽  
Slow Inactivation ◽  
Fast Inactivation ◽  
Α Subunit ◽  
Channel Inactivation ◽  
Sodium Channel Inactivation ◽  
Domain I

The role of the voltage sensor positive charges in fast and slow inactivation of the rat brain IIA sodium channel was investigated by mutating the second and fourth conserved positive charges in the S4 segments of all four homologous domains. Both charge-neutralizing mutations (by glutamine substitution) and charge-conserving mutations were constructed in a cDNA encoding the sodium channel α subunit. To determine if fast inactivation altered the effects of the mutations on slow inactivation, the mutations were also constructed in a channel that had fast inactivation removed by the incorporation of the IFMQ3 mutation in the III–IV linker (West, J.W., D.E. Patton, T. Scheuer, Y. Wang, A.L. Goldin, and W.A. Catterall. 1992. Proc. Natl. Acad. Sci. USA. 89:10910– 10914). Most of the mutations shifted the v1/2 of fast inactivation in the negative direction, with the largest effects resulting from mutations in domains I and II. These shifts were in the opposite direction compared with those observed for activation. The effects of the mutations on slow inactivation depended on whether fast inactivation was intact or not. When fast inactivation was eliminated, most of the mutations resulted in positive shifts in the v1/2 of slow inactivation. The largest effects again resulted from mutations in domains I and II. When fast inactivation was intact, the mutations in domains II and III resulted in negative shifts in the v1/2 of slow inactivation. Neutralization of the fourth charge in domain I or II resulted in the appearance of a second component in the voltage dependence of slow inactivation that was only observable when fast inactivation was intact. These results suggest the S4 regions of all four domains of the sodium channel are involved in the voltage dependence of inactivation, but to varying extents. Fast inactivation is not strictly coupled to activation, but it derives some independent voltage sensitivity from the charges in the S4 domains. Finally, there is an interaction between the fast and slow inactivation processes.

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.

A model of sodium channel inactivation based upon the modulated blocker

1983 ◽  
Vol 219 (1217) ◽  
pp. 423-438 ◽  
Keyword(s):  
Sodium Channel ◽  
Time Constant ◽  
Voltage Dependence ◽  
Physical Principle ◽  
Membrane Voltage ◽  
Displacement Current ◽  
Channel Inactivation ◽  
Gating Charge ◽  
Sodium Channel Inactivation ◽  
Activation Characteristic

An attempt is made to model sodium channel inactivation based upon real physical processes. The principle involved, which is supported by calculation and by direct appeal to experimental results, is that the gating dipole reversal or gating charge transfer that occurs when the channel is activated, markedly modulates the electrical properties of charged groups at the channel ends. Four examples of possible mechanisms that lead to channel inactivation are described. The simple four-state model that results is able to predict: ( а ) the steep voltage dependence of the equilibrium inactivation characteristic without the presence of any appreciable displacement current associated with inactivation; ( b ) the negative shift in membrane voltage of the equilibrium inactivation characteristic relative to the activation characteristic; ( c ) the bell-shaped dependence of inactivation time constant on membrane voltage; ( d ) the similarity of the membrane voltage dependence of the time constant of recovery from inactivation, to that of inactivation itself. A brief discussion of a model for sodium channel activation based upon the same physical principle is included.

scholarly journals Neutralization of Gating Charges in Domain II of the Sodium Channel α Subunit Enhances Voltage-Sensor Trapping by a β-Scorpion Toxin

2001 ◽  
Vol 118 (3) ◽  
pp. 291-302 ◽  
Author(s):  
Sandrine Cestèle ◽  
Todd Scheuer ◽  
Massimo Mantegazza ◽  
Hervé Rochat ◽  
William A. Catterall
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Voltage Dependence ◽  
Membrane Potentials ◽  
Voltage Sensor ◽  
Scorpion Toxin ◽  
Channel Activation ◽  
Α Subunit ◽  
Gating Charges

β-Scorpion toxins shift the voltage dependence of activation of sodium channels to more negative membrane potentials, but only after a strong depolarizing prepulse to fully activate the channels. Their receptor site includes the S3–S4 loop at the extracellular end of the S4 voltage sensor in domain II of the α subunit. Here, we probe the role of gating charges in the IIS4 segment in β-scorpion toxin action by mutagenesis and functional analysis of the resulting mutant sodium channels. Neutralization of the positively charged amino acid residues in the IIS4 segment by mutation to glutamine shifts the voltage dependence of channel activation to more positive membrane potentials and reduces the steepness of voltage-dependent gating, which is consistent with the presumed role of these residues as gating charges. Surprisingly, neutralization of the gating charges at the outer end of the IIS4 segment by the mutations R850Q, R850C, R853Q, and R853C markedly enhances β-scorpion toxin action, whereas mutations R856Q, K859Q, and K862Q have no effect. In contrast to wild-type, the β-scorpion toxin Css IV causes a negative shift of the voltage dependence of activation of mutants R853Q and R853C without a depolarizing prepulse at holding potentials from −80 to −140 mV. Reaction of mutant R853C with 2-aminoethyl methanethiosulfonate causes a positive shift of the voltage dependence of activation and restores the requirement for a depolarizing prepulse for Css IV action. Enhancement of sodium channel activation by Css IV causes large tail currents upon repolarization, indicating slowed deactivation of the IIS4 voltage sensor by the bound toxin. Our results are consistent with a voltage-sensor–trapping model in which the β-scorpion toxin traps the IIS4 voltage sensor in its activated position as it moves outward in response to depolarization and holds it there, slowing its inward movement on deactivation and enhancing subsequent channel activation. Evidently, neutralization of R850 and R853 removes kinetic barriers to binding of the IIS4 segment by Css IV, and thereby enhances toxin-induced channel activation.

scholarly journals Sodium Channel Activation Gating Is Affected by Substitutions of Voltage Sensor Positive Charges in All Four Domains

1997 ◽  
Vol 110 (4) ◽  
pp. 391-401 ◽  
Author(s):  
Kris J. Kontis ◽  
Amir Rounaghi ◽  
Alan L. Goldin
Keyword(s):  
Sodium Channel ◽  
Positive Charge ◽  
Voltage Dependence ◽  
Voltage Sensor ◽  
Positive Direction ◽  
Α Subunit ◽  
Positive Shift ◽  
Deactivation Kinetics ◽  
Maximal Activation ◽  
Domain Iii

The role of the voltage sensor positive charges in the activation and deactivation gating of the rat brain IIA sodium channel was investigated by mutating the second and fourth conserved positive charges in the S4 segments of all four homologous domains. Both charge-neutralizing (by glutamine substitution) and -conserving mutations were constructed in a cDNA encoding the sodium channel α subunit that had fast inactivation removed by the incorporation of the IFMQ3 mutation in the III–IV linker (West, J.W., D.E. Patton, T. Scheuer, Y. Wang, A.L. Goldin, and W.A. Catterall. 1992. Proc. Natl. Acad. Sci. USA. 89:10910–10914.). A total of 16 single and 2 double mutants were constructed and analyzed with respect to voltage dependence and kinetics of activation and deactivation. The most significant effects were observed with substitutions of the fourth positive charge in each domain. Neutralization of the fourth positive charge in domain I or II produced the largest shifts in the voltage dependence of activation, both in the positive direction. This change was accompanied by positive shifts in the voltage dependence of activation and deactivation kinetics. Combining the two mutations resulted in an even larger positive shift in half-maximal activation and a significantly reduced gating valence, together with larger positive shifts in the voltage dependence of activation and deactivation kinetics. In contrast, neutralization of the fourth positive charge in domain III caused a negative shift in the voltage of half-maximal activation, while the charge-conserving mutation resulted in a positive shift. Neutralization of the fourth charge in domain IV did not shift the half-maximal voltage of activation, but the conservative substitution produced a positive shift. These data support the idea that both charge and structure are determinants of function in S4 voltage sensors. Overall, the data supports a working model in which all four S4 segments contribute to voltage-dependent activation of the sodium channel.

scholarly journals Direct Evidence that Scorpion α-Toxins (Site-3) Modulate Sodium Channel Inactivation by Hindrance of Voltage-Sensor Movements

PLoS ONE ◽  
2013 ◽  
Vol 8 (11) ◽  
pp. e77758 ◽  
Author(s):  
Zhongming Ma ◽  
Jun Kong ◽  
Dalia Gordon ◽  
Michael Gurevitz ◽  
Roland G. Kallen
Keyword(s):  
Sodium Channel ◽  
Direct Evidence ◽  
Voltage Sensor ◽  
Channel Inactivation ◽  
Sodium Channel 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

Solution Structure of the Sodium Channel Inactivation Gate†,‡

Biochemistry ◽  
1999 ◽  
Vol 38 (3) ◽  
pp. 855-861 ◽  
Author(s):  
Carol A. Rohl ◽  
Faye A. Boeckman ◽  
Carl Baker ◽  
Todd Scheuer ◽  
William A. Catterall ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Solution Structure ◽  
Channel Inactivation ◽  
Sodium Channel Inactivation
Sign in / Sign up

Export Citation Format

Share Document