A Molecular Switch Driving Inactivation in the Cardiac K+ Channel hERG

Köpfer, David A.; Hahn, Ulrike; Ohmert, Iris; Vriend, Gert; Pongs, Olaf; Groot, Bert L. de; Zachariae, Ulrich

doi:10.1371/journal.pone.0041023

Cited by 20 publications

(15 citation statements)

References 59 publications

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“…A plausible explanation for this discrepancy is the existence of several binding modes for hERG blockers. This would also explain, why so many different hERG binding modes have been predicted in numerous previous studies 16 18 21 42 43 44 45 . The heterogeneous nature of drug binding in hERG might further explain why so many structurally diverse compounds can block this channel.…”

Section: Discussionmentioning

confidence: 63%

New potential binding determinant for hERG channel inhibitors

Saxena

Zangerl-Plessl

Linder

et al. 2016

Sci Rep

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Human ether-à-go-go related gene (hERG) 1 channels conduct the rapid delayed rectifier K + current (I Kr ) and are essential for the repolarization of the cardiac action potential. hERG1 inhibition by structurally diverse drugs may lead to life threatening arrhythmia. Putative binding determinants of hERG1 channel blockers include T623, S624 and V625 on the pore helix, and residues G648, Y652 and F656, located on segment S6. We and others have previously hypothesized that additional binding determinants may be located on helix S5, which is in close contact with the S6 segments. In order to test this hypothesis, we performed a detailed investigation combining ionic current measurements with two-microelectrode voltage clamp and molecular modeling techniques. We identified a novel aromatic high affinity binding determinant for blockers located in helix S5, F557, which is equally potent as Y652. Modeling supports a direct interaction with the outer pore helix.Human ether-à-go-go related gene (hERG) 1 channels conduct the rapid delayed rectifier K + current (I Kr ) and are essential for regulating the duration of the plateau phase of the cardiac action potential 1,2 . Inherited loss-of-function mutations in hERG1 can lead to life threatening torsades de pointes (TdP) arrhythmia 3 , while gain-of-function mutations are associated with short QT syndrome 4 . Most frequently, TdP arrhythmia is an acquired disorder, resulting from "off-target" block of this channel by structurally diverse drugs including antiarrhythmics, antihistamines, antipsychotics and antibiotics 5 . Since this inhibition can lead to sudden cardiac death, several pharmaceuticals such as cisapride or terfenadine were withdrawn from the market, or had their use severely restricted 6,7 . Recently, the Cardiac Safety Research Consortium (CSRC) and the Food and Drug Administration (FDA) proposed a new cardiac safety paradigm labelled "Comprehensive In Vitro Proarrhythmia Assay" (CiPA). The new CiPA guidelines emphasize the importance of studying pharmacological effects of drugs on three different ion channel types including hERG, Nav1.5 and Cav1.2, which proposed to play an important role in shaping the ventricular action potential 8 . hERG1 blockers might also have beneficial therapeutic potential. During routine preclinical screening for hERG1, new modulators, so-called activators, have been identified. These modulators may have the potential of shortening the action potential duration 9 . Thus, they might be beneficial for the treatment of inherited long QT syndrome.Great efforts have been directed toward a better understanding of the molecular and structural mechanisms of hERG1 channel drug interactions, including in vivo, in vitro and in silico approaches (for a recent reviews see Durdagi, S. et al. 10 and Vandenberg, J. et al. 11 ). Substantial progress has been made by identifying amino acids essential for drug block. The majority of hERG inhibitors are interacting with the pore module. This homo tetrameric module consists of an outer S5 helix, a...

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Section: Discussionmentioning

confidence: 63%

New potential binding determinant for hERG channel inhibitors

Saxena

Zangerl-Plessl

Linder

et al. 2016

Sci Rep

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“…In a more recent model, the collapsed (non‐conductive) state of the selectivity filter was most likely when the distance between the side chains of Ser620 and Asn629 was reduced to a distance that favoured formation of a bidentate H‐bond (Kopfer et al . ). In the S620T mutant, the additional methyl group adds steric bulk, which may alter a potential hydrogen bond network, whereas steric hindrance introduced by the disulphide bond formed between Cys628 and Cys631 prevents H‐bonding between Ser620 and Asn629.…”

Section: Discussionmentioning

confidence: 97%

Cooperative subunit interactions mediate fast C‐type inactivation of hERG1 K⁺ channels

Gardner

Sanguinetti

2014

The Journal of Physiology

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Key pointsr C-type inactivation of voltage-gated K + channels is caused by a conformational change in the selectivity filter that prevents ion conductance.r The role of subunit interaction during C-type inactivation of hERG1 K + channels was characterized by using concatenated tetrameric channels containing a defined composition and stoichiometry of wild-type subunits and subunits with a mutation known to attenuate or accentuate inactivation gating.r Analysis of the kinetics and voltage dependence of steady-state inactivation for the concatenated channels indicated a variable extent of subunit interaction, dependent on the location of the mutation used to probe the gating process.r Mutations located in the selectivity filter or pore helix disrupted inactivation in a dominant-negative manner, suggesting that the final step of C-type inactivation of hERG1 K + channels is mediated by a concerted, highly cooperative interaction between all four subunits.Abstract At depolarized membrane potentials, the conductance of some voltage-gated K + channels is reduced by C-type inactivation. This gating process is voltage independent in K v 1 and involves a conformational change in the selectivity filter that is mediated by cooperative subunit interactions. C-type inactivation in hERG1 K + channels is voltage-dependent, much faster in onset and greatly attenuates currents at positive potentials. Here we investigate the potential role of subunit interactions in C-type inactivation of hERG1 channels. Point mutations in hERG1 known to eliminate (G628C/S631C), inhibit (S620T or S631A) or enhance (T618A or M645C) C-type inactivation were introduced into subunits that were combined with wild-type subunits to form concatenated tetrameric channels with defined subunit composition and stoichiometry. Channels were heterologously expressed in Xenopus oocytes and the two-microelectrode voltage clamp was used to measure the kinetics and steady-state properties of inactivation of whole cell currents. The effect of S631A or T618A mutations on inactivation was a graded function of the number of mutant subunits within a concatenated tetramer as predicted by a sequential model of cooperative subunit interactions, whereas M645C subunits increased the rate of inactivation of concatemers, as predicted for subunits that act independently of one another. For mutations located within the inactivation gate proper (S620T or G628C/S631C), the presence of a single subunit in a concatenated hERG1 tetramer disrupted gating to the same extent as that observed for mutant homotetramers. Together, our findings indicate that the final step of C-type inactivation of hERG1 channels involves a concerted, all-or-none cooperative interaction between all four subunits, and that probing the mechanisms of channel gating with concatenated heterotypic channels should be interpreted with care, as conclusions regarding the nature of subunit interactions may depend on the specific mutation used to probe the gating process.

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“…Hydrogen bond networks around the SF have been implicated in C-type inactivation in different K + channels [ 11 , 13 , 15 ]. To test, if changed hydrogen bond networks behind the SF, led to conformational changes, enabling water leakage behind the SF, we monitored the hydrogen bonds between residues Y428, N441 and D398 as a function of time.…”

Section: Resultsmentioning

confidence: 99%

“…Numerous MD simulations on different K + channels have provided detailed insights into the behavior of the SF [ 10 , 12 , 13 , 23 – 27 ]. So far, no simulation studies have focused on the dynamics of the selectivity filter of the EAG1 channel.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of the EAG1 K + channel selectivity filter assessed by molecular dynamics simulations

Bernsteiner

Bründl

Stary-Weinzinger

2017

Biochemical and Biophysical Research Communications

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EAG1 channels belong to the KCNH family of voltage gated potassium channels. They are expressed in several brain regions and increased expression is linked to certain cancer types. Recent cryo-EM structure determination finally revealed the structure of these channels in atomic detail, allowing computational investigations. In this study, we performed molecular dynamics simulations to investigate the ion binding sites and the dynamical behavior of the selectivity filter. Our simulations suggest that sites S2 and S4 form stable ion binding sites, while ions placed at sites S1 and S3 rapidly switched to sites S2 and S4. Further, ions tended to dissociate away from S0 within less than 20 ns, due to increased filter flexibility. This was followed by water influx from the extracellular side, leading to a widening of the filter in this region, and likely non-conductive filter configurations. Simulations with the inactivation-enhancing mutant Y464A or Na ions lead to trapped water molecules behind the SF, suggesting that these simulations captured early conformational changes linked to C-type inactivation.

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A Molecular Switch Driving Inactivation in the Cardiac K+ Channel hERG

Cited by 20 publications

References 59 publications

New potential binding determinant for hERG channel inhibitors

New potential binding determinant for hERG channel inhibitors

Cooperative subunit interactions mediate fast C‐type inactivation of hERG1 K⁺ channels

Dynamics of the EAG1 K + channel selectivity filter assessed by molecular dynamics simulations

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A Molecular Switch Driving Inactivation in the Cardiac K+ Channel hERG

Cited by 20 publications

References 59 publications

New potential binding determinant for hERG channel inhibitors

New potential binding determinant for hERG channel inhibitors

Cooperative subunit interactions mediate fast C‐type inactivation of hERG1 K+ channels

Dynamics of the EAG1 K + channel selectivity filter assessed by molecular dynamics simulations

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Cooperative subunit interactions mediate fast C‐type inactivation of hERG1 K⁺ channels