Flavonoids and hERG channels: Friends or foes?

hERG (Human ether-a-go-go-related gene) potassium channel, which plays an essential role in cardiac action potential repolarization, is responsible for inherited and druginduced long QT syndrome. Recently, the Cryo-EM structure capturing the open conformation of hERG channel was determined, thus pushing the study on hERG channel at 3.8 Å resolution. This report focuses primarily on summarizing the design rationale and application of several fluorescent probes that target hERG channels, which enables dynamic and real-time monitoring of potassium pore channel affinity to further advance the understanding of the channels.

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Anti-tumor activity of a novel proteasome inhibitor D395 against multiple myeloma and its lower cardiotoxicity compared with carfilzomib

Cell Death and Disease ◽

10.1038/s41419-021-03701-z ◽

2021 ◽

Vol 12 (5) ◽

Author(s):

Xuxing Shen ◽

Chao Wu ◽

Meng Lei ◽

Qing Yan ◽

Haoyang Zhang ◽

...

Keyword(s):

Multiple Myeloma ◽

Proteasome Inhibitor ◽

Osteoclast Differentiation ◽

Dependent Manner ◽

Serum Enzyme ◽

Herg Channels ◽

Anti Tumor Activity ◽

Dose Dependent

AbstractCarfilzomib, a second-generation proteasome inhibitor, has significantly improved the survival rate of multiple myeloma (MM) patients, but its clinical application is still restricted by drug resistance and cardiotoxicity. Here, we identified a novel proteasome inhibitor, D395, and assessed its efficacy in treating MM as well as its cardiotoxicity at the preclinical level. The activities of purified and intracellular proteasomes were measured to determine the effect of D395 on the proteasome. CCK-8 and flow cytometry experiments were designed to evaluate the effects of D395 on cell growth and apoptosis. The effects of D395 and carfilzomib on serum enzyme activity, echocardiography features, cardiomyocyte morphology, and hERG channels were also compared. In our study, D395 was highly cytotoxic to MM cell lines and primary MM cells but not normal cells, and it was well tolerated in vivo. Similar to carfilzomib, D395 inhibited osteoclast differentiation in a dose-dependent manner. In particular, D395 exhibited lower cardiotoxicity than carfilzomib in all experiments. In conclusion, D395 is a novel irreversible proteasome inhibitor that has remarkable anti-MM activity and mild cardiotoxicity in vitro and in vivo.

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Hypoxia reduces mature hERG channels through calpain up‐regulation

The FASEB Journal ◽

10.1096/fj.201700255r ◽

2017 ◽

Vol 31 (11) ◽

pp. 5068-5077 ◽

Cited By ~ 9

Author(s):

Shawn M. Lamothe ◽

WonJu Song ◽

Jun Guo ◽

Wentao Li ◽

Tonghua Yang ◽

...

Keyword(s):

Herg Channels

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State‐dependent barium block of wild‐type and inactivation‐deficient HERG channels in Xenopus oocytes

The Journal of Physiology ◽

10.1111/j.1469-7793.2000.t01-1-00265.x ◽

2000 ◽

Vol 526 (2) ◽

pp. 265-278 ◽

Cited By ~ 17

Author(s):

Manjula Weerapura ◽

Stanley Nattel ◽

Marc Courtemanche ◽

David Doern ◽

Nathalie Ethier ◽

...

Keyword(s):

Xenopus Oocytes ◽

Wild Type ◽

State Dependent ◽

Barium Block ◽

Herg Channels

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Components of gating charge movement and S4 voltage-sensor exposure during activation of hERG channels

The Journal of General Physiology ◽

10.1085/jgp.201210942 ◽

2013 ◽

Vol 141 (4) ◽

pp. 431-443 ◽

Cited By ~ 16

Author(s):

Zhuren Wang ◽

Ying Dou ◽

Samuel J. Goodchild ◽

Zeineb Es-Salah-Lamoureux ◽

David Fedida

Keyword(s):

Mammalian Cells ◽

Voltage Sensor ◽

Delayed Rectifier ◽

Charge Movement ◽

Α Subunit ◽

Time Constants ◽

Gating Charge ◽

Activation Gating ◽

Pore Opening ◽

Herg Channels

The human ether-á-go-go–related gene (hERG) K+ channel encodes the pore-forming α subunit of the rapid delayed rectifier current, IKr, and has unique activation gating kinetics, in that the α subunit of the channel activates and deactivates very slowly, which focuses the role of IKr current to a critical period during action potential repolarization in the heart. Despite its physiological importance, fundamental mechanistic properties of hERG channel activation gating remain unclear, including how voltage-sensor movement rate limits pore opening. Here, we study this directly by recording voltage-sensor domain currents in mammalian cells for the first time and measuring the rates of voltage-sensor modification by [2-(trimethylammonium)ethyl] methanethiosulfonate chloride (MTSET). Gating currents recorded from hERG channels expressed in mammalian tsA201 cells using low resistance pipettes show two charge systems, defined as Q1 and Q2, with V1/2’s of −55.7 (equivalent charge, z = 1.60) and −54.2 mV (z = 1.30), respectively, with the Q2 charge system carrying approximately two thirds of the overall gating charge. The time constants for charge movement at 0 mV were 2.5 and 36.2 ms for Q1 and Q2, decreasing to 4.3 ms for Q2 at +60 mV, an order of magnitude faster than the time constants of ionic current appearance at these potentials. The voltage and time dependence of Q2 movement closely correlated with the rate of MTSET modification of I521C in the outermost region of the S4 segment, which had a V1/2 of −64 mV and time constants of 36 ± 8.5 ms and 11.6 ± 6.3 ms at 0 and +60 mV, respectively. Modeling of Q1 and Q2 charge systems showed that a minimal scheme of three transitions is sufficient to account for the experimental findings. These data point to activation steps further downstream of voltage-sensor movement that provide the major delays to pore opening in hERG channels.

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A Place for High-Throughput Electrophysiology in Cardiac Safety: Screening hERG Cell Lines and Novel Compounds with the Ion Works HTTM System

CrossRef Listing of Deleted DOIs ◽

10.1177/1087057105280566 ◽

2005 ◽

Vol 10 (8) ◽

pp. 832-840 ◽

Cited By ~ 26

Author(s):

Heather Guthrie ◽

Frederick S. Livingston ◽

Ueli Gubler ◽

Ralph Garippa

Keyword(s):

Cell Line ◽

Cell Lines ◽

Torsades De Pointes ◽

Delayed Rectifier ◽

Drug Candidates ◽

Delayed Rectifier Potassium Channel ◽

A Cell ◽

Line Selection ◽

Herg Channels ◽

Cell Line Selection

Several commercially available pharmaceutical compounds have been shown to block the I Krcurrent of the cardiac action potential. This effect can cause a prolongation of the electrocardiogram QTinterval and a delay in ventricular repolarization. The Food and Drug Administration recommends that all new potential drug candidates be assessed for I Krblock to avoid a potentially lethal cardiac arrhythmia known as torsades de pointes. Direct compound interaction with the human ether-a-go-go– related gene (hERG) product, a delayed rectifier potassium channel, has been identified as a molecular mechanism of I Kr block. One strategy to identify compounds withh ERGliability is to monitor hERGcurrent inhibition using electrophysiology techniques. The authors describe the Ion Works HT ™instrument as a tool for screening cell lines expressing hERG channels. Based on current amplitude and stability criteria, a cell line was selected and used to perform a 300-compound screen. The screen was able to identify compounds with hERG activity within projects that spanned different therapeutic areas. The cell line selection and optimization, as well as the screening abilities of the Ion Works HT ™system, provide a powerful means of assessinghERGactive compounds early in the drug discovery pipeline.

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Ceramide modulates HERG potassium channel gating by translocation into lipid rafts

AJP Cell Physiology ◽

10.1152/ajpcell.00462.2009 ◽

2010 ◽

Vol 299 (1) ◽

pp. C74-C86 ◽

Cited By ~ 19

Author(s):

Sindura B. Ganapathi ◽

Todd E. Fox ◽

Mark Kester ◽

Keith S. Elmslie

Keyword(s):

Potassium Channels ◽

Action Potential ◽

Lipid Rafts ◽

Negative Impact ◽

Cardiac Action Potential ◽

Cholesterol Depletion ◽

Cardiac Action ◽

Herg Channels ◽

The Impact ◽

Action Potential Repolarization

Human ether-à-go-go-related gene (HERG) potassium channels play an important role in cardiac action potential repolarization, and HERG dysfunction can cause cardiac arrhythmias. However, recent evidence suggests a role for HERG in the proliferation and progression of multiple types of cancers, making it an attractive target for cancer therapy. Ceramide is an important second messenger of the sphingolipid family, which due to its proapoptotic properties has shown promising results in animal models as an anticancer agent . Yet the acute effects of ceramide on HERG potassium channels are not known. In the present study we examined the effects of cell-permeable C6-ceramide on HERG potassium channels stably expressed in HEK-293 cells. C6-ceramide (10 μM) reversibly inhibited HERG channel current (IHERG) by 36 ± 5%. Kinetically, ceramide induced a significant hyperpolarizing shift in the current-voltage relationship (Δ V1/2 = −8 ± 0.5 mV) and increased the deactivation rate (43 ± 3% for τfast and 51 ± 3% for τslow). Mechanistically, ceramide recruited HERG channels within caveolin-enriched lipid rafts. Cholesterol depletion and repletion experiments and mathematical modeling studies confirmed that inhibition and gating effects are mediated by separate mechanisms. The ceramide-induced hyperpolarizing gating shift (raft mediated) could offset the impact of inhibition (raft independent) during cardiac action potential repolarization, so together they may nullify any negative impact on cardiac rhythm. Our results provide new insights into the effects of C6-ceramide on HERG channels and suggest that C6-ceramide can be a promising therapeutic for cancers that overexpress HERG.

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