Differential effect of D623N variant and wild-type Nav1.7 sodium channels on resting potential and interspike membrane potential of dorsal root ganglion neurons

Ahn, Hye-Sook; Vasylyev, Dmytro V.; Estacion, Mark; Macala, Lawrence J.; Shah, Palak; Faber, Catharina G.; Merkies, Ingemar S. J.; Dib‐Hajj, Sulayman D.; Waxman, Stephen G.

doi:10.1016/j.brainres.2013.07.005

Cited by 16 publications

(16 citation statements)

References 38 publications

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“…For current-voltage relationship, cells were hold at –120 mV and stepped to a range of test voltages (–140 to +40 mV in 5 mV increments) for 100 ms. Maximal inward currents were plotted as a function of test voltage to generate the current-voltage plot. We made a regression line of the currents points between +10 and +40 mV in the current-voltage plots of each cell [ 22 , 35 , 36 , 59 – 64 ], while the maximal Na + currents usually appear at a test voltage between 0 and –20 mV. The reversal potential of Na + (V rev; Na + ) was determined by extrapolating the regression line to the transverse axis, and the maximal Na + conductance (G max ) was given by the product of ΔV (the difference between each voltage and the reversal potential) and the slope of the regression line from each individual cell.…”

Section: Methodsmentioning

confidence: 99%

“…The measured currents at each voltage were divided by the maximal currents at each voltage in the same cell to give G/G max . The activation data were then fitted with a Boltzmann function: G/G max = 1/(1+exp(V h –V)/ k )), where G max is the maximal Na + conductance, V h is the potential at which activation is half-maximal, V is the test voltage in mV, and k is the slope factor [ 22 , 35 , 36 , 59 – 64 ]. For the steady-state fast inactivation curve, we measured the currents at a +10 mV test pulse after 100 ms prepulse at different potentials from a holding potential of –120 mV.…”

Section: Methodsmentioning

confidence: 99%

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The Biophysical Basis Underlying Gating Changes in the p.V1316A Mutant Nav1.7 Channel and the Molecular Pathogenesis of Inherited Erythromelalgia

et al. 2016

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The Nav1.7 channel critically contributes to the excitability of sensory neurons, and gain-of-function mutations of this channel have been shown to cause inherited erythromelalgia (IEM) with neuropathic pain. In this study, we report a case of a severe phenotype of IEM caused by p.V1316A mutation in the Nav1.7 channel. Mechanistically, we first demonstrate that the Navβ4 peptide acts as a gating modifier rather than an open channel blocker competing with the inactivating peptide to give rise to resurgent currents in the Nav1.7 channel. Moreover, there are two distinct open and two corresponding fast inactivated states in the genesis of resurgent Na+ currents. One is responsible for the resurgent route and practically existent only in the presence of Navβ4 peptide, whereas the other is responsible for the “silent” route of recovery from inactivation. In this regard, the p.V1316A mutation makes hyperpolarization shift in the activation curve, and depolarization shift in the inactivation curve, vividly uncoupling inactivation from activation. In terms of molecular gating operation, the most important changes caused by the p.V1316A mutation are both acceleration of the transition from the inactivated states to the activated states and deceleration of the reverse transition, resulting in much larger sustained as well as resurgent Na+ currents. In summary, the genesis of the resurgent currents in the Nav1.7 channel is ascribable to the transient existence of a distinct and novel open state promoted by the Navβ4 peptide. In addition, S4–5 linker in domain III where V1316 is located seems to play a critical role in activation–inactivation coupling, chiefly via direct modulation of the transitional kinetics between the open and the inactivated states. The sustained and resurgent Na+ currents may therefore be correlatively enhanced by specific mutations involving this linker and relevant regions, and thus marked hyperexcitability in corresponding neural tissues as well as IEM symptomatology.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The Biophysical Basis Underlying Gating Changes in the p.V1316A Mutant Nav1.7 Channel and the Molecular Pathogenesis of Inherited Erythromelalgia

et al. 2016

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“…170,171,173 Gain-of-function variants that shift activation of Na v 1.7 in a hyperpolarizing direction, slow deactivation, and enhance ramp currents cause IEM. Over 20 different IEM variants have been discovered in Na v 1.7, and almost all variants investigated so far result in a hyperpolarizing shift of activation, allowing Na v 1.7 to open at lower potentials compared with the wild type, [174][175][176][177][178][179][180][181][182][183][184][185][186][187] in familial cases, 175,[188][189][190] and children. 178,191 This left shift of activation enhances excitability, intuitively explaining the pain phenotype.…”

Section: Voltage-gated Sodium Channelopathies In Sfnmentioning

confidence: 99%

Small‐fiber neuropathy: Expanding the clinical pain universe

Sopacua

Hoeijmakers

Merkies

et al. 2019

J Peripheral Nervous Sys

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Small‐fiber neuropathy (SFN) is a disorder of thinly myelinated Aδ and unmyelinated C fibers. SFN is clinically dominated by neuropathic pain and autonomic complaints, leading to a significant reduction in quality of life. According to international criteria, the diagnosis is established by the assessment of intraepidermal nerve fiber density and/or quantitative sensory testing. SFN is mainly associated with autoimmune diseases, sodium channel gene variants, diabetes mellitus, and vitamin B12 deficiencies, although in more than one half of patients no etiology can be identified. Recently, gain‐of‐function variants in the genes encoding for the Nav1.7, Nav1.8 and Nav1.9 sodium channel subunits have been discovered in SFN patients, enlarging the spectrum of underlying conditions. Sodium channel gene variants associated with SFN can lead to a diversity of phenotypes, including different pain distributions and presence or absence of autonomic symptoms. This suggests that SFN is part of a clinical continuum. New assessments might contribute to a better understanding of the cellular and molecular substrates of SFN and might provide improved diagnostic methods and trial designs in the future. Identification of the underlying mechanisms may inform the development of drugs that more effectively address neuropathic pain and autonomic symptoms of SFN.

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“…Dynamic-clamp recording. DRG neurons (soma diameter 21-26 m; 24.4 Ϯ 0.3, n ϭ 25) obtained from postnatal day 0-5 Sprague-Dawley rats were grown in primary culture for 2-3 days (Ahn et al 2013;Dib-Hajj et al 2009). Small DRG neurons were dynamically clamped (Kemenes et al 2011;Samu et al 2012;Sharp et al 1993) in whole cell configuration using patch pipettes pulled from glass capillaries (cat.…”

mentioning

confidence: 99%

Dynamic-clamp analysis of wild-type human Na_v1.7 and erythromelalgia mutant channel L858H

Vasylyev

Han

Zhao

et al. 2014

Journal of Neurophysiology

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The link between sodium channel Nav1.7 and pain has been strengthened by identification of gain-of-function mutations in patients with inherited erythromelalgia (IEM), a genetic model of neuropathic pain in humans. A firm mechanistic link to nociceptor dysfunction has been precluded because assessments of the effect of the mutations on nociceptor function have thus far depended on electrophysiological recordings from dorsal root ganglia (DRG) neurons transfected with wild-type (WT) or mutant Nav1.7 channels, which do not permit accurate calibration of the level of Nav1.7 channel expression. Here, we report an analysis of the function of WT Nav1.7 and IEM L858H mutation within small DRG neurons using dynamic-clamp. We describe the functional relationship between current threshold for action potential generation and the level of WT Nav1.7 conductance in primary nociceptive neurons and demonstrate the basis for hyperexcitability at physiologically relevant levels of L858H channel conductance. We demonstrate that the L858H mutation, when modeled using dynamic-clamp at physiological levels within DRG neurons, produces a dramatically enhanced persistent current, resulting in 27-fold amplification of net sodium influx during subthreshold depolarizations and even greater amplification during interspike intervals, which provide a mechanistic basis for reduced current threshold and enhanced action potential firing probability. These results show, for the first time, a linear correlation between the level of Nav1.7 conductance and current threshold in DRG neurons. Our observations demonstrate changes in sodium influx that provide a mechanistic link between the altered biophysical properties of a mutant Nav1.7 channel and nociceptor hyperexcitability underlying the pain phenotype in IEM.

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Differential effect of D623N variant and wild-type Nav1.7 sodium channels on resting potential and interspike membrane potential of dorsal root ganglion neurons

Cited by 16 publications

References 38 publications

The Biophysical Basis Underlying Gating Changes in the p.V1316A Mutant Nav1.7 Channel and the Molecular Pathogenesis of Inherited Erythromelalgia

The Biophysical Basis Underlying Gating Changes in the p.V1316A Mutant Nav1.7 Channel and the Molecular Pathogenesis of Inherited Erythromelalgia

Small‐fiber neuropathy: Expanding the clinical pain universe

Dynamic-clamp analysis of wild-type human Na_v1.7 and erythromelalgia mutant channel L858H

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Differential effect of D623N variant and wild-type Nav1.7 sodium channels on resting potential and interspike membrane potential of dorsal root ganglion neurons

Cited by 16 publications

References 38 publications

The Biophysical Basis Underlying Gating Changes in the p.V1316A Mutant Nav1.7 Channel and the Molecular Pathogenesis of Inherited Erythromelalgia

The Biophysical Basis Underlying Gating Changes in the p.V1316A Mutant Nav1.7 Channel and the Molecular Pathogenesis of Inherited Erythromelalgia

Small‐fiber neuropathy: Expanding the clinical pain universe

Dynamic-clamp analysis of wild-type human Nav1.7 and erythromelalgia mutant channel L858H

Contact Info

Product

Resources

About

Dynamic-clamp analysis of wild-type human Na_v1.7 and erythromelalgia mutant channel L858H