scholarly journals Differential Modulation of Fast Inactivation in Cardiac Sodium Channel Splice Variants by Fyn Tyrosine Kinase

2015 ◽  
Vol 37 (3) ◽  
pp. 825-837 ◽  
Author(s):  
Shahid M. Iqbal ◽  
Gowri S.B. Andavan ◽  
Rosa Lemmens-Gruber
Keyword(s):  
Tyrosine Kinase ◽  
Sodium Channel ◽  
Splice Variants ◽  
Ionic Currents ◽  
Differential Modulation ◽  
Fast Inactivation ◽  
Fyn Kinase ◽  
Cardiac Sodium Channel ◽  
Hyperpolarizing Shift ◽  
Fyn Tyrosine Kinase

Background/Aims: Post-translational modifications such as phosphorylation and dephosphorylation can finely tune the function of ion channels. Nav1.5 is the main sodium channel in human hearts and alternative splicing of the transcript generates two major splice variants, characterized by the presence (Q-pre) or absence (Q-del) of glutamine at position 1077. In the heart, both the Nav1.5 channel and Fyn tyrosine kinase are colocalized at adherens junctions. This study aimed to investigate the modulation of the aforementioned splice variants by Fyn tyrosine kinase. Methods and Results: Q-del and Q-pre were transiently expressed alone, with catalytically active Fyn kinase (FynKa) or with a catalytically dead Fyn kinase (FynKd). Co-expression of Nav1.5 channel splice variants and Fyn kinase was confirmed by Western blotting and their Interaction was established by co-immunoprecipitation experiments. The enzymatic activity of Fyn kinase and phosphorylation of Nav1.5 channel were ascertained by immunoprecipitation and anti-phosphotyrosine immunoblotting. Whole-cell ionic currents were recorded in patch clamp experiments to examine the modulation of Nav1.5 channel variants by Fyn kinase, which indicated a hyperpolarizing shift of 9.68 mV in fast inactivation of Q-del. In contrast, a depolarizing shift of 8.77 mV in fast inactivation was observed in the case of Q-pre, while activation curves remained unaltered for both splice variants. This differential modulation in fast inactivation was further assessed by mutating tyrosine 1495 to phenylalanine in the inactivation loop, which completely removed the modulatory effect of Fyn kinase in Q-pre splice variant, while in Q-del variant hyperpolarizing shift in fast inactivation was reduced to 4.74 mV. Finally, the modulatory effect of Fyn kinase was compensated at a mid-value of 94.63 ± 0.34, when both splice variants were co-expressed at a normal physiological ratio. Conclusion: Q-del and Q-pre were differentially modulated by Fyn kinase, and this fine modification resulted in smooth electrical activity in the heart.

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 Modulation of the Cardiac Sodium Channel Na V 1.5 by Fyn, a Src Family Tyrosine Kinase

2005 ◽  
Vol 96 (9) ◽  
pp. 991-998 ◽  
Author(s):  
Christopher A. Ahern ◽  
Ji-Fang Zhang ◽  
Marilyn J. Wookalis ◽  
Richard Horn
Keyword(s):  
Tyrosine Kinase ◽  
Sodium Channel ◽  
Cardiac Sodium Channel

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.

Effects of Halothane and Isoflurane on Fast and Slow Inactivation of Human Heart hH1a Sodium Channels

1999 ◽  
Vol 90 (6) ◽  
pp. 1671-1683. ◽  
Author(s):  
Anna Stadnicka ◽  
Wai-Meng Kwok ◽  
Hali A. Hartmann ◽  
Zeljko J. Bosnjak
Keyword(s):  
Steady State ◽  
Heterologous Expression ◽  
Sodium Channel ◽  
Sodium Channels ◽  
Human Heart ◽  
Sodium Current ◽  
Volatile Anesthetic ◽  
Slow Inactivation ◽  
Fast Inactivation ◽  
Cardiac Sodium Channel

Background Cloning and heterologous expression of ion channels allow biophysical and molecular studies of the mechanisms of volatile anesthetic interactions with human heart sodium channels. Volatile anesthetics may influence the development of arrhythmias arising from cardiac sodium channel dysfunction. For that reason, understanding the mechanisms of interactions between these anesthetics and cardiac sodium channels is important. This study evaluated the mechanisms of volatile anesthetic actions on the cloned human cardiac sodium channel (hH1a) alpha subunit. Methods Inward sodium currents were recorded from human embryonic kidney (HEK293) cells stably expressing hH1a channels. The effects of halothane and isoflurane on current and channel properties were evaluated using the whole cell voltage-clamp technique. Results Halothane at 0.47 and 1.1 mM and isoflurane at 0.54 and 1.13 mM suppressed the sodium current in a dose- and voltage-dependent manner. Steady state activation was not affected, but current decay was accelerated. The voltage dependence of steady state fast and slow inactivations was shifted toward more hyperpolarized potentials. The slope factor of slow but not fast inactivation curves was reduced significantly. Halothane increased the time constant of recovery from fast inactivation. The recovery from slow inactivation was not affected significantly by either anesthetic. Conclusions In a heterologous expression system, halothane and isoflurane interact with the hH1a channels and suppress the sodium current. The mechanisms involve acceleration of the transition from the open to the inactivated state, stabilization of the fast and slow inactivated states, and prolongation of the inactivated state by delayed recovery from the fast inactivated to the resting state.

scholarly journals Fyn tyrosine kinase is a downstream mediator of Rho/PRK2 function in keratinocyte cell–cell adhesion

2002 ◽  
Vol 156 (1) ◽  
pp. 137-148 ◽  
Author(s):  
Enzo Calautti ◽  
Maddalena Grossi ◽  
Cristina Mammucari ◽  
Yumi Aoyama ◽  
Maria Pirro ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Kinase Activation ◽  
Positive Effects ◽  
Fyn Kinase ◽  
Keratinocyte Cell ◽  
Downstream Mediator ◽  
Cell Cell ◽  
Fyn Tyrosine Kinase

The Rho GTPase and Fyn tyrosine kinase have been implicated previously in positive control of keratinocyte cell–cell adhesion. Here, we show that Rho and Fyn operate along the same signaling pathway. Endogenous Rho activity increases in differentiating keratinocytes and is required for both Fyn kinase activation and increased tyrosine phosphorylation of β- and γ-catenin, which is associated with the establishment of keratinocyte cell–cell adhesion. Conversely, expression of constitutive active Rho is sufficient to promote cell–cell adhesion through a tyrosine kinase- and Fyn-dependent mechanism, trigger Fyn kinase activation, and induce tyrosine phosphorylation of β- and γ-catenin and p120ctn. The positive effects of activated Rho on cell–cell adhesion are not induced by an activated Rho mutant with defective binding to the serine/threonine PRK2/PKN kinases. Endogenous PRK2 kinase activity increases with keratinocyte differentiation, and, like activated Rho, increased PRK2 activity promotes keratinocyte cell–cell adhesion and induces tyrosine phosphorylation of β- and γ-catenin and Fyn kinase activation. Thus, these findings reveal a novel role of Fyn as a downstream mediator of Rho in control of keratinocyte cell–cell adhesion and implicate the PRK2 kinase, a direct Rho effector, as a link between Rho and Fyn activation.

Biochemical and biophysical studies of the interaction of class I antiarrhythmic drugs with the cardiac sodium channel

1994 ◽  
Vol 33 (3) ◽  
pp. 277-294 ◽  
Author(s):  
Gerald W. Zamponi ◽  
Henry J. Duff ◽  
Robert J. French ◽  
Robert S. Sheldon
Keyword(s):  
Sodium Channel ◽  
Antiarrhythmic Drugs ◽  
Class I ◽  
Cardiac Sodium Channel ◽  
Biophysical Studies

Differential effects of cardiac sodium channel mutations on initiation of ventricular arrhythmias in patients with Brugada syndrome

Heart Rhythm ◽  
2009 ◽  
Vol 6 (4) ◽  
pp. 487-492 ◽  
Author(s):  
Hiroshi Morita ◽  
Satoshi Nagase ◽  
Daiji Miura ◽  
Aya Miura ◽  
Shigeki Hiramatsu ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Brugada Syndrome ◽  
Ventricular Arrhythmias ◽  
Differential Effects ◽  
Cardiac Sodium Channel
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