Voltage-dependent gating of KCNH potassium channels lacking a covalent link between voltage-sensing and pore domains

Lörinczi, Éva; Gómez-Posada, Juan Camilo; Peña, Pilar de la; Tomczak, Adam P.; Fernández-Trillo, Jorge; Leipscher, Ulrike; Stühmer, Walter; Barros, Francisco; Pardo, Luis A.

doi:10.1038/ncomms7672

Cited by 85 publications

(132 citation statements)

References 60 publications

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“…The recent cryo-EM structure of the eag channel reveals that the S4-S5 linker in eag, and related channels such as hERG, may be too short to function as a mechanical lever that influences the pore gate (6). This idea is supported by the observation that activation gating is not strongly influenced in channels in which the physical connection between the S4-S5 linker and the pore domain is disrupted (7).…”

Section: S4-s5 Linker Coupling During Deactivationsupporting

confidence: 57%

“…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%

“…Here, we have used mutation of G546 in the S4-S5 linker as a perturbation tool to investigate the role of the S4-S5 linker in deactivation gating. We were further driven to investigate the S4-S5 linker by the observation that disruption of the physical connection between the voltage sensor and pore domains, while not influencing activation greatly, impacted deactivation gating significantly (7). Furthermore, evidence from Shaker channels suggests that the S4-S5 linker couples the pore and voltage sensor during deactivation based on the observation that specific interactions between residues in the S4-S5 linker and the pore control mode-shift behavior (24).…”

Section: S4-s5 Linker Coupling During Deactivationmentioning

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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Section: S4-s5 Linker Coupling During Deactivationsupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Section: S4-s5 Linker Coupling During Deactivationmentioning

confidence: 99%

See 1 more Smart Citation

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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“…In other words, this gate is intrinsically more stable in the open state. Surprisingly, hERG pore domain construct (S5-S6) alone, isolated from the voltage sensor domain, gives rise to a nonfunctional channel 19 . One particularity for hERG, compared to the aforementioned bacterial channels, is that the cytosolic N-terminus deletion greatly accelerates deactivation [24][25][26] .…”

Section: Discussionmentioning

confidence: 99%

hERG S4-S5 linker acts as a voltage-dependent ligand that binds to the activation gate and locks it in a closed state

Malak¹,

Es‐Salah‐Lamoureux²,

Loussouarn³

2017

Archives of Cardiovascular Diseases Supplements

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Delayed-rectifier potassium channels (hERG and KCNQ1) play a major role in cardiac repolarization. These channels are formed by a tetrameric pore (S5-S6) surrounded by four voltage sensor domains (S1-S4). Coupling between voltage sensor domains and the pore activation gate is critical for channel voltage-dependence. However, molecular mechanisms remain elusive. Herein, we demonstrate that covalently binding, through a disulfide bridge, a peptide mimicking the S4-S5 linker (S4-S5 L ) to the channel S6 C-terminus (S6 T ) completely inhibits hERG. This shows that channel S4-S5 L is sufficient to stabilize the pore activation gate in its closed state. Conversely, covalently binding a peptide mimicking S6 T to the channel S4-S5 L prevents its inhibiting effect and renders the channel almost completely voltage-independent. This shows that the channel S4-S5 L is necessary to stabilize the activation gate in its closed state. Altogether, our results provide chemical evidence that S4-S5 L acts as a voltagecontrolled ligand that binds S6 T to lock the channel in a closed state, elucidating the coupling between voltage sensors and the gate in delayed rectifier potassium channels and potentially other voltagegated channels.Voltage-dependent ion channels are ubiquitously expressed in human tissues. They perform a plethora of physiological functions such as generation and modulation of the electrical activity in excitable tissues, modulation of neurotransmitter and hormone release, and electrolyte transport in epithelia. Canonical voltage-gated ion channels are tetramers of subunits containing six transmembrane segments (S1 to S6). Each of the four subunits is composed of one voltage sensor domain (S1 to S4) and a pore domain (S5-S6). The four pore domains tetramerize to generate a single pore module, which is regulated by the four voltage sensor domains 1, 2 . One key question remains: how do the voltage sensor domains regulate pore gating? Several independent approaches support the idea that interaction between the S4-S5 linker (S4-S5 L ) and the S6 C-terminal (S6 T ) part plays a critical role in that regulation [2][3][4][5] . First, Lu and collaborators pinpointed the sequence complementarity between S4-S5 L and S6 T in the Shaker channel 4,5 . Second, structural data indicated the close proximity between S4-S5 L and S6 T and suggested a mechanical lever model to explain the coupling between the voltage sensor and the gate of the related K v 1.2 channel 2 . However, the mechanism may prove to be more complex. Since 2006, several works on other eukaryotic K v channels suggested state-dependent S4-S5 L and S6 T interactions 3,[6][7][8][9][10] , but the precise mechanism remains elusive and may vary from one channel to another.In a previous study, we suggested that the voltage dependence of the cardiac voltage-gated KCNQ1 channel (K v 7.1) follows a ligand/receptor model. In this model, S4-S5 L is a ligand whose interaction with S6 T is only possible at resting potentials, and this interaction locks the channel in a closed s...

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“…Most recently, fusion of the VSD of Ci-VSP to the viral channel Kcv created a functional voltage-gated K + channel [46]. Notably, the S4-S5 linker is not required for voltage-dependent gating of KCNH potassium channels, suggesting that the voltage sensing could be transduced between the pore and VSD modules in the absence of covalent linker [47]. Although a single VSD can sense the changes of membrane potential and function independently [48][49][50], swapping the full-length VSD among 4-fold symmetric voltage-sensitive channels or transplanting the full-length VSD to the monomeric VSP failed to obtain functional proteins [40,51].…”

Section: Discussionmentioning

confidence: 99%

Grafting voltage and pharmacological sensitivity in potassium channels

Lan

Fan

et al. 2016

Cell Res

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A classical voltage-gated ion channel consists of four voltage-sensing domains (VSDs). However, the roles of each VSD in the channels remain elusive. We developed a GVTDT (Graft VSD To Dimeric TASK3 channels that lack endogenous VSDs) strategy to produce voltage-gated channels with a reduced number of VSDs. TASK3 channels exhibit a high host tolerance to VSDs of various voltage-gated ion channels without interfering with the intrinsic properties of the TASK3 selectivity filter. The constructed channels, exemplified by the channels grafted with one or two VSDs from Kv7.1 channels, exhibit classical voltage sensitivity, including voltage-dependent opening and closing. Furthermore, the grafted Kv7.1 VSD transfers the potentiation activity of benzbromarone, an activator that acts on the VSDs of the donor channels, to the constructed channels. Our study indicates that one VSD is sufficient to voltage-dependently gate the pore and provides new insight into the roles of VSDs.

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Voltage-dependent gating of KCNH potassium channels lacking a covalent link between voltage-sensing and pore domains

Cited by 85 publications

References 60 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

hERG S4-S5 linker acts as a voltage-dependent ligand that binds to the activation gate and locks it in a closed state

Grafting voltage and pharmacological sensitivity in potassium channels

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