Human ether-a-go-go related gene (hERG) K+ channels: Function and dysfunction
ABSTRACT The human Ether-a-go-go Related Gene (hERG) potassium channel plays a central role in regulating cardiac excitability and maintenance of normal cardiac rhythm. Mutations in hERG cause a third of all cases of congenital long QT syndrome, a disorder of cardiac repolarisation characterised by prolongation of the QT interval on the surface electrocardiogram, abnormal T waves, and a risk of sudden cardiac death due to ventricular arrhythmias. Additionally, the hERG channel protein is the molecular target for almost all drugs that cause the acquired form of long QT syndrome. Advances in understanding the structural basis of hERG gating, its traffic to the cell surface, and the molecular architecture involved in drug-block of hERG, are providing the foundation for rational treatment and prevention of hERG associated long QT syndrome. This review summarises the current knowledge of hERG function and dysfunction, and the areas of ongoing research.
- SourceAvailable from: Amalendu P Ranjan
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- "The corrected current with heart rate is defined as QTc . This IKr or the hERG current is critical for ventricular repolarization and inhibition of IKr can induce QT prolongation which may result in life threatening ventricular arrhythmias . "
ABSTRACT: Cardiac toxicity is the foremost reason for drug discontinuation from development to clinical evaluation and post market surveillance [Fung 35:293-317, 2001; Piccini 158:317-326 2009]. The Food and Drug Administration (FDA) has rejected many potential pharmaceutical agents due to QT prolongation effects. Since drug development and FDA approval takes an enormous amount of time, money and effort with high failure rates, there is an increased focus on rescuing drugs that cause QT prolongation. If these otherwise safe and potent drugs were formulated in a unique way so as to mitigate the QT prolongation associated with them, these potent drugs may get FDA approval for clinical use. Rescuing these compounds not only benefit the patients who need them but also require much less time and money thus leading to faster clinical translation. In this study, we chose curcumin as our drug of choice since it has been shown to posses anti-tumor properties against various cancers with limited toxicity. The major limitations with this pharmacologically active drug are (a) its ability to prolong QT by inhibiting the hERG channel and (b) its low bioavailability. In our previous studies, we found that lipids have protective actions against hERG channel inhibition and therefore QT prolongation. Results of the manual patch clamp assay of HEK 293 cells clearly illustrated that our hybrid nanocurcumin formulation prevented the curcumin induced inhibition of hERG K+ channel at concentrations higher than the therapeutic concentrations of curcumin. Comparing the percent inhibition, the hybrid nanocurcumin limited inhibition to 24.8% at a high curcumin equivalent concentration of 18 muM. Liposomal curcumin could only decrease this inhibition upto 30% only at lower curcumin concentration of 6 muM but not at 18 muM concentration. Here we show a curcumin encapsulated lipopolymeric hybrid nanoparticle formulation which could protect against QT prolongation and also render increased bioavailability and stability thereby overcoming the limitations associated with curcumin.Journal of Nanobiotechnology 12/2013; 11(1):40. DOI:10.1186/1477-3155-11-40 · 4.12 Impact Factor
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- "This cardiac potassium channel is voltage-activated. It has a relatively large inner cavity that allows drug molecules to enter and bind tightly to the channel pore   . Aromatic amino acid residues arranged in two rings of four amino acids each within the central cavity enhance interactions with aromatic groups of drugs and thus may lead to channel blockage, prevent potassium conduction, and eventually cause the drug-acquired LQTS [17e21]. "
ABSTRACT: The human Ether-a-go-go-Related-Gene (hERG) potassium (K(+)) channel is liable to drug-inducing blockage that prolongs the QT interval of the cardiac action potential, triggers arrhythmia and possibly causes sudden cardiac death. Early prediction of drug liability to hERG K(+) channel is therefore highly important and preferably obligatory at earlier stages of any drug discovery process. In vitro assessment of drug binding affinity to hERG K(+) channel involves substantial expenses, time, and labor; and therefore computational models for predicting liabilities of drug candidates for hERG toxicity is of much importance. In the present study, we apply the Iterative Stochastic Elimination (ISE) algorithm to construct a large number of rule-based models (filters) and exploit their combination for developing the concept of hERG Toxicity Index (ETI). ETI estimates the molecular risk to be a blocker of hERG potassium channel. The area under the curve (AUC) of the attained model is 0.94. The averaged ETI of hERG binders, drugs from CMC, clinical-MDDR, endogenous molecules, ACD and ZINC, were found to be 9.17, 2.53, 3.3, -1.98, -2.49 and -3.86 respectively. Applying the proposed hERG Toxicity Index Model on external test set composed of more than 1300 hERG blockers picked from chEMBL shows excellent performance (Matthews Correlation Coefficient of 0.89). The proposed strategy could be implemented for the evaluation of chemicals in the hit/lead optimization stages of the drug discovery process, improve the selection of drug candidates as well as the development of safe pharmaceutical products.European Journal of Medicinal Chemistry 05/2013; 65C:304-314. DOI:10.1016/j.ejmech.2013.04.059 · 3.45 Impact Factor
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- "It is lined by many unique aromatic residues that are absent in most other K channels. These optimally positioned aromatic residues and the polar residues are an integral part of the unique binding sites for diverse pharmacologic agents [Perry et al. 2010; Perrin et al. 2008; Kannankeril, 2008]. "
ABSTRACT: The prolonged QT interval is both widely seen and associated with the potentially deadly rhythm, Torsades de Pointes (TdP). While it can occur spontaneously in the congenital form, there is a wide array of drugs that have been implicated in the prolongation of the QT interval. Some of these drugs have either been restricted or withdrawn from the market due to the increased incidence of fatal polymorphic ventricular tachycardia. The list of drugs that cause QT prolongation continues to grow, and an updated list of specific drugs that prolong the QT interval can be found at www.qtdrugs.org. This review focuses on the mechanism of drug-induced QT prolongation, risk factors for TdP, culprit drugs, prevention and monitoring of prolonged drug-induced QT prolongation and treatment strategies.Therapeutic Advances in Drug Safety 10/2012; 3(5):241-253. DOI:10.1177/2042098612454283