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Alkanols inhibit voltage-gated K(+) channels via a distinct gating modifying mechanism that prevents gate opening.

Martínez-Morales E, Kopljar I, Snyders DJ, Labro AJ - Sci Rep (2015)

Bottom Line: Using the non-conducting Shaker-W434F mutant, we found that both alkanols immobilized approximately 10% of the gating charge and accelerated the deactivating gating currents simultaneously with ionic current inhibition.Thus, alkanols prevent the final VSD movement(s) that is associated with channel gate opening.Drug competition experiments showed that alkanols do not share the binding site of 4-aminopyridine, a drug that exerts a similar effect at the gating current level.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, Antwerp, 2610, Belgium.

ABSTRACT
Alkanols are small aliphatic compounds that inhibit voltage-gated K(+) (K(v)) channels through a yet unresolved gating mechanism. K(v) channels detect changes in the membrane potential with their voltage-sensing domains (VSDs) that reorient and generate a transient gating current. Both 1-Butanol (1-BuOH) and 1-Hexanol (1-HeOH) inhibited the ionic currents of the Shaker K(v) channel in a concentration dependent manner with an IC50 value of approximately 50 mM and 3 mM, respectively. Using the non-conducting Shaker-W434F mutant, we found that both alkanols immobilized approximately 10% of the gating charge and accelerated the deactivating gating currents simultaneously with ionic current inhibition. Thus, alkanols prevent the final VSD movement(s) that is associated with channel gate opening. Applying 1-BuOH and 1-HeOH to the Shaker-P475A mutant, in which the final gating transition is isolated from earlier VSD movements, strengthened that neither alkanol affected the early VSD movements. Drug competition experiments showed that alkanols do not share the binding site of 4-aminopyridine, a drug that exerts a similar effect at the gating current level. Thus, alkanols inhibit Shaker-type K(v) channels via a unique gating modifying mechanism that stabilizes the channel in its non-conducting activated state.

No MeSH data available.


Related in: MedlinePlus

1-BuOH and 4-AP immobilize the same gating charge component.(A) Superposition of steady-state IGdeac recordings of Shaker-IR-W434F, elicited during a repolarizing step to -120 mV upon a 50 ms depolarization at 0 mV, in control condition (light gray), in presence of 1 mM 4-AP (dark gray), and in presence of 1 mM 4-AP plus 300 mM 1-BuOH (black). Note that the mixture of 4-AP plus 1-BuOH did not result in an extra acceleration of IGdeac decay or an extra reduction in gating charge movement. (B) Panel shows τIGac and τIGdeac in control condition (white circles, n = 6), in presence of 4-AP (dark gray squares, n = 5), and 4-AP plus 1-BuOH mixture (black circles, n = 6). Both drug conditions resulted in a similar acceleration of τIGdeac without affecting τIGac markedly.
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f5: 1-BuOH and 4-AP immobilize the same gating charge component.(A) Superposition of steady-state IGdeac recordings of Shaker-IR-W434F, elicited during a repolarizing step to -120 mV upon a 50 ms depolarization at 0 mV, in control condition (light gray), in presence of 1 mM 4-AP (dark gray), and in presence of 1 mM 4-AP plus 300 mM 1-BuOH (black). Note that the mixture of 4-AP plus 1-BuOH did not result in an extra acceleration of IGdeac decay or an extra reduction in gating charge movement. (B) Panel shows τIGac and τIGdeac in control condition (white circles, n = 6), in presence of 4-AP (dark gray squares, n = 5), and 4-AP plus 1-BuOH mixture (black circles, n = 6). Both drug conditions resulted in a similar acceleration of τIGdeac without affecting τIGac markedly.

Mentions: The impact of 1-BuOH and 1-HeOH on the IG recordings of the Shaker-IR-W434F channel was reminiscent of the effect of 4-AP that prevents the channels from passing the late subunit-cooperative step of channel gate opening, resulting in a similar 10% reduction in gating charge movement14. To assess if 4-AP and 1-BuOH immobilized the same gating charge component, we determined the reduction in gating charge movement using a mixture of 1 mM 4-AP and 300 mM 1-BuOH, which for both compounds are saturating concentrations. First, we applied 1 mM 4-AP that resulted in an approximately 10% loss of gating charge movement and an acceleration of τIGdeac, as has been described before1423. After establishing a steady-state 4-AP effect, we applied 300 mM 1-BuOH in the continued presence of 1 mM 4-AP. The addition of 1-BuOH did not result in an extra reduction of gating charge movement or further acceleration of the IGdeac kinetics (Fig. 5). This indicated that both compounds affected the same gating charge component and further supported that alkanols stabilize the channel in the non-conducting activated state similar to 4-AP.


Alkanols inhibit voltage-gated K(+) channels via a distinct gating modifying mechanism that prevents gate opening.

Martínez-Morales E, Kopljar I, Snyders DJ, Labro AJ - Sci Rep (2015)

1-BuOH and 4-AP immobilize the same gating charge component.(A) Superposition of steady-state IGdeac recordings of Shaker-IR-W434F, elicited during a repolarizing step to -120 mV upon a 50 ms depolarization at 0 mV, in control condition (light gray), in presence of 1 mM 4-AP (dark gray), and in presence of 1 mM 4-AP plus 300 mM 1-BuOH (black). Note that the mixture of 4-AP plus 1-BuOH did not result in an extra acceleration of IGdeac decay or an extra reduction in gating charge movement. (B) Panel shows τIGac and τIGdeac in control condition (white circles, n = 6), in presence of 4-AP (dark gray squares, n = 5), and 4-AP plus 1-BuOH mixture (black circles, n = 6). Both drug conditions resulted in a similar acceleration of τIGdeac without affecting τIGac markedly.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663795&req=5

f5: 1-BuOH and 4-AP immobilize the same gating charge component.(A) Superposition of steady-state IGdeac recordings of Shaker-IR-W434F, elicited during a repolarizing step to -120 mV upon a 50 ms depolarization at 0 mV, in control condition (light gray), in presence of 1 mM 4-AP (dark gray), and in presence of 1 mM 4-AP plus 300 mM 1-BuOH (black). Note that the mixture of 4-AP plus 1-BuOH did not result in an extra acceleration of IGdeac decay or an extra reduction in gating charge movement. (B) Panel shows τIGac and τIGdeac in control condition (white circles, n = 6), in presence of 4-AP (dark gray squares, n = 5), and 4-AP plus 1-BuOH mixture (black circles, n = 6). Both drug conditions resulted in a similar acceleration of τIGdeac without affecting τIGac markedly.
Mentions: The impact of 1-BuOH and 1-HeOH on the IG recordings of the Shaker-IR-W434F channel was reminiscent of the effect of 4-AP that prevents the channels from passing the late subunit-cooperative step of channel gate opening, resulting in a similar 10% reduction in gating charge movement14. To assess if 4-AP and 1-BuOH immobilized the same gating charge component, we determined the reduction in gating charge movement using a mixture of 1 mM 4-AP and 300 mM 1-BuOH, which for both compounds are saturating concentrations. First, we applied 1 mM 4-AP that resulted in an approximately 10% loss of gating charge movement and an acceleration of τIGdeac, as has been described before1423. After establishing a steady-state 4-AP effect, we applied 300 mM 1-BuOH in the continued presence of 1 mM 4-AP. The addition of 1-BuOH did not result in an extra reduction of gating charge movement or further acceleration of the IGdeac kinetics (Fig. 5). This indicated that both compounds affected the same gating charge component and further supported that alkanols stabilize the channel in the non-conducting activated state similar to 4-AP.

Bottom Line: Using the non-conducting Shaker-W434F mutant, we found that both alkanols immobilized approximately 10% of the gating charge and accelerated the deactivating gating currents simultaneously with ionic current inhibition.Thus, alkanols prevent the final VSD movement(s) that is associated with channel gate opening.Drug competition experiments showed that alkanols do not share the binding site of 4-aminopyridine, a drug that exerts a similar effect at the gating current level.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, Antwerp, 2610, Belgium.

ABSTRACT
Alkanols are small aliphatic compounds that inhibit voltage-gated K(+) (K(v)) channels through a yet unresolved gating mechanism. K(v) channels detect changes in the membrane potential with their voltage-sensing domains (VSDs) that reorient and generate a transient gating current. Both 1-Butanol (1-BuOH) and 1-Hexanol (1-HeOH) inhibited the ionic currents of the Shaker K(v) channel in a concentration dependent manner with an IC50 value of approximately 50 mM and 3 mM, respectively. Using the non-conducting Shaker-W434F mutant, we found that both alkanols immobilized approximately 10% of the gating charge and accelerated the deactivating gating currents simultaneously with ionic current inhibition. Thus, alkanols prevent the final VSD movement(s) that is associated with channel gate opening. Applying 1-BuOH and 1-HeOH to the Shaker-P475A mutant, in which the final gating transition is isolated from earlier VSD movements, strengthened that neither alkanol affected the early VSD movements. Drug competition experiments showed that alkanols do not share the binding site of 4-aminopyridine, a drug that exerts a similar effect at the gating current level. Thus, alkanols inhibit Shaker-type K(v) channels via a unique gating modifying mechanism that stabilizes the channel in its non-conducting activated state.

No MeSH data available.


Related in: MedlinePlus