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Mutation I136V alters electrophysiological properties of the Na(v)1.7 channel in a family with onset of erythromelalgia in the second decade.

Cheng X, Dib-Hajj SD, Tyrrell L, Waxman SG - Mol Pain (2008)

Bottom Line: In this study, we characterized the gating and kinetic properties of I136V mutant channels in HEK293 cells using whole-cell patch clamp.I136V also decreases the deactivation rate, and generates larger ramp currents.The I136V substitution in Na(v)1.7 alters channel gating and kinetic properties.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.

ABSTRACT

Background: Primary erythromelalgia is an autosomal dominant pain disorder characterized by burning pain and skin redness in the extremities, with onset of symptoms during the first decade in the families whose mutations have been physiologically studied to date. Several mutations of voltage-gated Na+ channel NaV1.7 have been linked with primary erythromelalgia. Recently, a new substitution Na(v)1.7/I136V has been reported in a Taiwanese family, in which pain appeared at later ages (9-22 years, with onset at 17 years of age or later in 5 of 7 family members), with relatively slow progression (8-10 years) to involvement of the hands. The proband reported onset of symptoms first in his feet at the age of 11, which then progressed to his hands at the age of 19. The new mutation is located in transmembrane segment 1 (S1) of domain I (DI) in contrast to all Na(v)1.7 mutations reported to date, which have been localized in the voltage sensor S4, the linker joining segments S4 and S5 or pore-lining segments S5 and S6 in DI, II and III.

Results: In this study, we characterized the gating and kinetic properties of I136V mutant channels in HEK293 cells using whole-cell patch clamp. I136V shifts the voltage-dependence of activation by -5.7 mV, a smaller shift in activation than the other erythromelalgia mutations that have been characterized. I136V also decreases the deactivation rate, and generates larger ramp currents.

Conclusion: The I136V substitution in Na(v)1.7 alters channel gating and kinetic properties. Each of these changes may contribute to increased excitability of nociceptive dorsal root ganglion neurons, which underlies pain in erythromelalgia. The smaller shift in voltage-dependence of activation of Na(v)1.7, compared to the other reported cases of inherited erythromelalgia, may contribute to the later age of onset and slower progression of the symptoms reported in association with this mutation.

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I136V mutation alters recovery from fast-inactivation and increases currents elicited by slow ramp depolarizations. A, Cells were held at -100 mV, and fast-inactivation was initiated by a 20-ms depolarization to 0 mV, followed by a recovery period (2–300 ms) at a recovery potential, followed by a 10-ms test pulse to 0 mV to measure the available channels. Recovery rate were calculated by comparing the peak currents of test pulse to prepulse at 0 mV (20 ms) after various recovery durations (2–300 ms) at different recovery potentials (-100, -90, -80, and -70 mV), and plotted as a function of recovery potentials. Recovery time constants of NaV1.7R and I136V mutant channels were then estimated using single-exponential fits. At a recovery potential of -70 mV, I136V mutant channels (n = 11) recovered faster than wild type NaV1.7R channels (n = 12). B, Representative ramp currents from NaV1.7R (black) and I136V mutant (gray) channels. HEK293 cells were held at -100 mV and a depolarizing voltage ramp from -100 mV to +20 mV was applied at a rate of 0.2 mV/ms. The insert shows mean ramp currents of wild type NaV1.7R and I136V mutant channels. Currents were normalized to the maximal peak currents from step depolarizations in Figure 1B. I136V mutant channels were activated at more negative potentials and generated larger ramp currents than NaV1.7R channels (NaV1.7R: 0.23 ± 0.02, n = 19; I136V: 0.79 ± 0.04, n = 26, p < 0.05).
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Figure 3: I136V mutation alters recovery from fast-inactivation and increases currents elicited by slow ramp depolarizations. A, Cells were held at -100 mV, and fast-inactivation was initiated by a 20-ms depolarization to 0 mV, followed by a recovery period (2–300 ms) at a recovery potential, followed by a 10-ms test pulse to 0 mV to measure the available channels. Recovery rate were calculated by comparing the peak currents of test pulse to prepulse at 0 mV (20 ms) after various recovery durations (2–300 ms) at different recovery potentials (-100, -90, -80, and -70 mV), and plotted as a function of recovery potentials. Recovery time constants of NaV1.7R and I136V mutant channels were then estimated using single-exponential fits. At a recovery potential of -70 mV, I136V mutant channels (n = 11) recovered faster than wild type NaV1.7R channels (n = 12). B, Representative ramp currents from NaV1.7R (black) and I136V mutant (gray) channels. HEK293 cells were held at -100 mV and a depolarizing voltage ramp from -100 mV to +20 mV was applied at a rate of 0.2 mV/ms. The insert shows mean ramp currents of wild type NaV1.7R and I136V mutant channels. Currents were normalized to the maximal peak currents from step depolarizations in Figure 1B. I136V mutant channels were activated at more negative potentials and generated larger ramp currents than NaV1.7R channels (NaV1.7R: 0.23 ± 0.02, n = 19; I136V: 0.79 ± 0.04, n = 26, p < 0.05).

Mentions: The ability of channels to recover from fast inactivation (repriming) may determine how fast a neuron can repetitively fire. Repriming kinetics of wild type and mutant channels were examined for a series of recovery periods at four different recovery potentials between prepulses and test pulses. I136V mutation does not change the repriming kinetics at -100, -90, and -80 mV, but significantly enhances the recovery at -70 mV (Figure 3A).


Mutation I136V alters electrophysiological properties of the Na(v)1.7 channel in a family with onset of erythromelalgia in the second decade.

Cheng X, Dib-Hajj SD, Tyrrell L, Waxman SG - Mol Pain (2008)

I136V mutation alters recovery from fast-inactivation and increases currents elicited by slow ramp depolarizations. A, Cells were held at -100 mV, and fast-inactivation was initiated by a 20-ms depolarization to 0 mV, followed by a recovery period (2–300 ms) at a recovery potential, followed by a 10-ms test pulse to 0 mV to measure the available channels. Recovery rate were calculated by comparing the peak currents of test pulse to prepulse at 0 mV (20 ms) after various recovery durations (2–300 ms) at different recovery potentials (-100, -90, -80, and -70 mV), and plotted as a function of recovery potentials. Recovery time constants of NaV1.7R and I136V mutant channels were then estimated using single-exponential fits. At a recovery potential of -70 mV, I136V mutant channels (n = 11) recovered faster than wild type NaV1.7R channels (n = 12). B, Representative ramp currents from NaV1.7R (black) and I136V mutant (gray) channels. HEK293 cells were held at -100 mV and a depolarizing voltage ramp from -100 mV to +20 mV was applied at a rate of 0.2 mV/ms. The insert shows mean ramp currents of wild type NaV1.7R and I136V mutant channels. Currents were normalized to the maximal peak currents from step depolarizations in Figure 1B. I136V mutant channels were activated at more negative potentials and generated larger ramp currents than NaV1.7R channels (NaV1.7R: 0.23 ± 0.02, n = 19; I136V: 0.79 ± 0.04, n = 26, p < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 3: I136V mutation alters recovery from fast-inactivation and increases currents elicited by slow ramp depolarizations. A, Cells were held at -100 mV, and fast-inactivation was initiated by a 20-ms depolarization to 0 mV, followed by a recovery period (2–300 ms) at a recovery potential, followed by a 10-ms test pulse to 0 mV to measure the available channels. Recovery rate were calculated by comparing the peak currents of test pulse to prepulse at 0 mV (20 ms) after various recovery durations (2–300 ms) at different recovery potentials (-100, -90, -80, and -70 mV), and plotted as a function of recovery potentials. Recovery time constants of NaV1.7R and I136V mutant channels were then estimated using single-exponential fits. At a recovery potential of -70 mV, I136V mutant channels (n = 11) recovered faster than wild type NaV1.7R channels (n = 12). B, Representative ramp currents from NaV1.7R (black) and I136V mutant (gray) channels. HEK293 cells were held at -100 mV and a depolarizing voltage ramp from -100 mV to +20 mV was applied at a rate of 0.2 mV/ms. The insert shows mean ramp currents of wild type NaV1.7R and I136V mutant channels. Currents were normalized to the maximal peak currents from step depolarizations in Figure 1B. I136V mutant channels were activated at more negative potentials and generated larger ramp currents than NaV1.7R channels (NaV1.7R: 0.23 ± 0.02, n = 19; I136V: 0.79 ± 0.04, n = 26, p < 0.05).
Mentions: The ability of channels to recover from fast inactivation (repriming) may determine how fast a neuron can repetitively fire. Repriming kinetics of wild type and mutant channels were examined for a series of recovery periods at four different recovery potentials between prepulses and test pulses. I136V mutation does not change the repriming kinetics at -100, -90, and -80 mV, but significantly enhances the recovery at -70 mV (Figure 3A).

Bottom Line: In this study, we characterized the gating and kinetic properties of I136V mutant channels in HEK293 cells using whole-cell patch clamp.I136V also decreases the deactivation rate, and generates larger ramp currents.The I136V substitution in Na(v)1.7 alters channel gating and kinetic properties.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.

ABSTRACT

Background: Primary erythromelalgia is an autosomal dominant pain disorder characterized by burning pain and skin redness in the extremities, with onset of symptoms during the first decade in the families whose mutations have been physiologically studied to date. Several mutations of voltage-gated Na+ channel NaV1.7 have been linked with primary erythromelalgia. Recently, a new substitution Na(v)1.7/I136V has been reported in a Taiwanese family, in which pain appeared at later ages (9-22 years, with onset at 17 years of age or later in 5 of 7 family members), with relatively slow progression (8-10 years) to involvement of the hands. The proband reported onset of symptoms first in his feet at the age of 11, which then progressed to his hands at the age of 19. The new mutation is located in transmembrane segment 1 (S1) of domain I (DI) in contrast to all Na(v)1.7 mutations reported to date, which have been localized in the voltage sensor S4, the linker joining segments S4 and S5 or pore-lining segments S5 and S6 in DI, II and III.

Results: In this study, we characterized the gating and kinetic properties of I136V mutant channels in HEK293 cells using whole-cell patch clamp. I136V shifts the voltage-dependence of activation by -5.7 mV, a smaller shift in activation than the other erythromelalgia mutations that have been characterized. I136V also decreases the deactivation rate, and generates larger ramp currents.

Conclusion: The I136V substitution in Na(v)1.7 alters channel gating and kinetic properties. Each of these changes may contribute to increased excitability of nociceptive dorsal root ganglion neurons, which underlies pain in erythromelalgia. The smaller shift in voltage-dependence of activation of Na(v)1.7, compared to the other reported cases of inherited erythromelalgia, may contribute to the later age of onset and slower progression of the symptoms reported in association with this mutation.

Show MeSH
Related in: MedlinePlus