Functional Impact of BeKm-1, a High-Affinity hERG Blocker, on Cardiomyocytes Derived from Human-Induced Pluripotent Stem Cells

Abstract

IKr current, a major component of cardiac repolarization, is mediated by human Ether-à-go-go-Related Gene (hERG, Kv11.1) potassium channels. The blockage of these channels by pharmacological compounds is associated to drug-induced long QT syndrome (LQTS), which is a life-threatening disorder characterized by ventricular arrhythmias and defects in cardiac repolarization that can be illustrated using cardiomyocytes derived from human-induced pluripotent stem cells (hiPS-CMs). This study was meant to assess the modification in hiPS-CMs excitability and contractile properties by BeKm-1, a natural scorpion venom peptide that selectively interacts with the extracellular face of hERG, by opposition to reference compounds that act onto the intracellular face. Using an automated patch-clamp system, we compared the affinity of BeKm-1 for hERG channels with some reference compounds. We fully assessed its effects on the electrophysiological, calcium handling, and beating properties of hiPS-CMs. By delaying cardiomyocyte repolarization, the peptide induces early afterdepolarizations and reduces spontaneous action potentials, calcium transients, and contraction frequencies, therefore recapitulating several of the critical phenotype features associated with arrhythmic risk in drug-induced LQTS. BeKm-1 exemplifies an interesting reference compound in the integrated hiPS-CMs cell model for all drugs that may block the hERG channel from the outer face. Being a peptide that is easily modifiable, it will serve as an ideal molecular platform for the design of new hERG modulators displaying additional functionalities.

Optical control of cardiac rhythm byin vivophotoactivation of an ERG channel peptide inhibitor

“…Uncaging of BeKm-1 is also prone to induce early-afterdepolarization in 47% of the cells (Figure 3f-g). In a layer of spontaneously beating hiPS-derived cardiomyocytes, we report that uncaging of BeKm-1 induces slowing of automaticity and dysrhythmia (Figure 3h), which is coherent with earlier observations using non-caged BeKm-1 23 . These results demonstrate the ability to control hERG currents by UV illumination in several cell models.…”

“…Single-cell dissociated hiPS-CMs were plated at low density on matrigel-coated 35mm Petri dishes (Nunc) and electrophysiological experiments were performed 12-14 days after plating. APs were recorded at 37°C in the current-clamp mode using the dynamic patch-clamp method to electronically mimic expression of the inward rectifier potassium current, IK1 23,36,37 . Two pA/pF in silico IK1 density (maximum density on the current-voltage curve at -72 mV) was sufficient to bring the resting membrane potential and AP duration at different times of repolarization (APD).…”

“…For this first proof-ofprinciple demonstration, we first sought to test this technology for its ability to regulate heart rhythm. To achieve this, we chose to target the ERG channel (Kv11.1) with a natural peptide, BeKm-1, a 36 amino-acid peptide with three disulfide bridges originally isolated from the venom of Buthus eupeus scorpion 19 , which has both an exquisite selectivity and nanomolar potency for Kv11.1 [19][20][21][22][23] . In healthy tissues, this channel is expressed in the sino-atrial node (SAN) where it controls, along with other channel types, pacemaker action potential and rhythmicity [24][25][26][27][28][29][30] .…”

Genetic and Molecular Aspects of Drug-Induced QT Interval Prolongation

“…An example of this state-dependent blockade was shown by the BeKm-1 scorpion toxin, which exhibits high selectivity and affinity for hERG channels in the closed state. BeKm-1 blocks the channel through a pore obstruction mechanism, with subsequent proarrhythmic effects in a rabbit’s heart [ 57 ]. Nevertheless, the majority of drugs that exhibit high-affinity blockade show preferential binding to the inactivated state.…”

Peptides for Health Benefits 2020

“…Moreover, its ability to activate sperm motility from a variety of species (including humans) through the interaction with the receptor that controls motility function was proven. De Waard et al [ 21 ] explore the biological effects of BeKm-1, a natural scorpion venom peptide. By delaying cardiomyocyte repolarization, BeKm-1 induces early afterdepolarizations and reduces spontaneous action potentials, calcium transients, and contraction frequencies.…”