Regional flexibility in the S4–S5 linker regulates hERG channel closed-state stabilization

Hull, Christina M.; Sokolov, S. D.; Slyke, Aaron C. Van; Claydon, Tom W.

doi:10.1007/s00424-013-1431-9

Cited by 19 publications

(35 citation statements)

References 29 publications

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“…Mode-shift has been reported in hERG channels (2,10,11,13), but is dependent on recording conditions. This makes comparison of the effects of mutations challenging.…”

Section: Characterization Of Mode-shift Behavior In Herg Channelsmentioning

confidence: 91%

“…This process would be expected to alter the energetic landscape experienced by the voltage sensor during its return upon repolarization. Indeed, what has been called mode-shift behavior of hERG channels has been documented in a number of studies (2,10,11,13). These studies present, however, differing reports of the extent of mode-shift and the effects of, for example, deletion of the N-terminus.…”

Section: Characterization Of Mode-shift Behavior In Herg Channelsmentioning

confidence: 99%

“…Several studies have suggested that the S4-S5 linker that connects the voltage sensor domain with the pore domain is involved in the coupling of charge movement with pore gate opening (1)(2)(3)(4)(5)33). However, recent evidence suggests that the mechanism of coupling in hERG channels may be different from that in other Shaker-like Kv channels.…”

Section: S4-s5 Linker Coupling During Deactivationmentioning

confidence: 99%

“…Numerous studies support a role for the hERG S4-S5 linker in transducing voltage sensor motions to the pore gate (1)(2)(3)(4)(5); however, recent structural (6) and functional (7) evidence suggests that voltage sensing may be coupled to the pore in hERG by an alternate mechanism that is divergent from Shaker-like Kv channels.…”

Section: Introductionmentioning

confidence: 99%

“…This results in a separation of the voltage dependencies of activation and deactivation such that more energy is required to return channels to the deactivated state than to activate them (2,(8)(9)(10)(11)(12)(13). Stabilization or immobilization of voltage sensor charges has been observed in a number of channels in response to depolarization and this can be mediated by factors outside of the voltage sensor, such as the N-type inactivation particle or other intracellular pore blockers that prevent closure of the pore gate (14,15), the permeant ion species (16), or inactivation (17,18).…”

Section: Introductionmentioning

confidence: 99%

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Stabilization of the Activated hERG Channel Voltage Sensor by Depolarization Involves the S4-S5 Linker

Thouta

Hull

Shi

et al. 2017

Biophysical Journal

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Slow deactivation of hERG channels is critical for preventing cardiac arrhythmia yet the mechanistic basis for the slow gating transition is unclear. Here, we characterized the temporal sequence of events leading to voltage sensor stabilization upon membrane depolarization. Progressive increase in step depolarization duration slowed voltage-sensor return in a biphasic manner (t fast ¼ 34 ms, t slow ¼ 2.5 s). The faster phase of voltage-sensor return slowing correlated with the kinetics of pore opening. The slower component occurred over durations that exceeded channel activation and was consistent with voltage sensor relaxation. The S4-S5 linker mutation, G546L, impeded the faster phase of voltage sensor stabilization without attenuating the slower phase, suggesting that the S4-S5 linker is important for communications between the pore gate and the voltage sensor during deactivation. These data also demonstrate that the mechanisms of pore gate-opening-induced and relaxation-induced voltage-sensor stabilization are separable. Deletion of the distal N-terminus (D2-135) accelerated off-gating current, but did not influence the relative contribution of either mechanism of stabilization of the voltage sensor. Lastly, we characterized mode-shift behavior in hERG channels, which results from stabilization of activated channel states. The apparent mode-shift depended greatly on recording conditions. By measuring slow activation and deactivation at steady state we found the ''true'' mode-shift to be~15 mV. Interestingly, the ''true'' mode-shift of gating currents was~40 mV, much greater than that of the pore gate. This demonstrates that voltage sensor return is less energetically favorable upon repolarization than pore gate closure. We interpret this to indicate that stabilization of the activated voltage sensor limits the return of hERG channels to rest. The data suggest that this stabilization occurs as a result of reconfiguration of the pore gate upon opening by a mechanism that is influenced by the S4-S5 linker, and by a separable voltage-sensor intrinsic relaxation mechanism.

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“…Mode-shift has been reported in hERG channels (2,10,11,13), but is dependent on recording conditions. This makes comparison of the effects of mutations challenging.…”

Section: Characterization Of Mode-shift Behavior In Herg Channelsmentioning

confidence: 91%

Section: Characterization Of Mode-shift Behavior In Herg Channelsmentioning

confidence: 99%

Section: S4-s5 Linker Coupling During Deactivationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Stabilization of the Activated hERG Channel Voltage Sensor by Depolarization Involves the S4-S5 Linker

Thouta

Hull

Shi

et al. 2017

Biophysical Journal

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Conservation analysis of residues in the S4–S5 linker and the terminal part of the S5-P-S6 pore modulus in Kv and HCN channels: flexible determinants for the electromechanical coupling

Balleza

Carrillo

Gómez-Lagunas

2014

Pflugers Arch - Eur J Physiol

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Protein mobility is important to achieve protein function. Intrinsic flexibility associated with motion underlies this important issue and the analysis of side chain flexibility gives insights to understand it. In this work, the S5-P-S6 pore modulus (PM) of members of Kv and HCN channels was examined by a combination of sequence alignment, residue composition analysis, and intrinsic side chain flexibility. The PM sequences were organized as a database that was used to reveal and correlate the functional diversity of each analyzed family. Specifically, we focused our attention on the crucial role of the S4-S5 linker and its well-described interaction with the S6 T during the electromechanical coupling. Our analysis suggests the presence of a Gly-hinge in the middle of the S4-S5 linkers. This apparent Gly-hinge links a flexible N-terminal segment with a rigid C-terminal one, although in Kv7 channels, the latter segment is even more flexible. Instead, HCN channels exhibit a putative Thr-hinge and is rich in aromatic residues, in consequence, their linker is more rigid. Concerning S6, we confirm the presence of the two flexible kinks previously described and we provide the complete segmental flexibility profiles for the different families. Our results are discussed in terms of the relation between residue composition, conservation, and local conformational flexibility. This provides important insights to understand and differentiate the characteristic gating properties of these channels as well as their implications in cell physiology.

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Gating mechanism of Kv11.1 (hERG) K+ channels without covalent connection between voltage sensor and pore domains

Peña

Domı́nguez

Barros

2017

Pflugers Arch - Eur J Physiol

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Kv11.1 (hERG, KCNH2) is a voltage-gated potassium channel crucial in setting the cardiac rhythm and the electrical behaviour of several non-cardiac cell types. Voltage-dependent gating of Kv11.1 can be reconstructed from non-covalently linked voltage sensing and pore modules (split channels), challenging classical views of voltage-dependent channel activation based on a S4–S5 linker acting as a rigid mechanical lever to open the gate. Progressive displacement of the split position from the end to the beginning of the S4–S5 linker induces an increasing negative shift in activation voltage dependence, a reduced z g value and a more negative ΔG 0 for current activation, an almost complete abolition of the activation time course sigmoid shape and a slowing of the voltage-dependent deactivation. Channels disconnected at the S4–S5 linker near the S4 helix show a destabilization of the closed state(s). Furthermore, the isochronal ion current mode shift magnitude is clearly reduced in the different splits. Interestingly, the progressive modifications of voltage dependence activation gating by changing the split position are accompanied by a shift in the voltage-dependent availability to a methanethiosulfonate reagent of a Cys introduced at the upper S4 helix. Our data demonstrate for the first time that alterations in the covalent connection between the voltage sensor and the pore domains impact on the structural reorganizations of the voltage sensor domain. Also, they support the hypothesis that the S4–S5 linker integrates signals coming from other cytoplasmic domains that constitute either an important component or a crucial regulator of the gating machinery in Kv11.1 and other KCNH channels.Electronic supplementary materialThe online version of this article (10.1007/s00424-017-2093-9) contains supplementary material, which is available to authorized users.

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Regional flexibility in the S4–S5 linker regulates hERG channel closed-state stabilization

Cited by 19 publications

References 29 publications

Stabilization of the Activated hERG Channel Voltage Sensor by Depolarization Involves the S4-S5 Linker

Stabilization of the Activated hERG Channel Voltage Sensor by Depolarization Involves the S4-S5 Linker

Conservation analysis of residues in the S4–S5 linker and the terminal part of the S5-P-S6 pore modulus in Kv and HCN channels: flexible determinants for the electromechanical coupling

Gating mechanism of Kv11.1 (hERG) K+ channels without covalent connection between voltage sensor and pore domains

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