Abstract
Voltage-gated ion channels (VGCs) are prime targets for the pharmaceutical industry, but drug profiling on VGCs is challenging, since drug interactions are confined to specific conformational channel states mediated by changes in transmembrane potential. Here we combined various optogenetic tools to develop dynamic, high-throughput drug profiling assays with defined light-step protocols to interrogate VGC states on a millisecond timescale. We show that such light-induced electrophysiology (LiEp) yields high-quality pharmacological data with exceptional screening windows for drugs acting on the major cardiac VGCs, including hNav1.5, hKv1.5 and hERG. LiEp-based screening remained robust when using a variety of optogenetic actuators (ChR2, ChR2(H134R), CatCh, ChR2-EYFP-βArchT) and different types of organic (RH421, Di-4-ANBDQPQ, BeRST1) or genetic voltage sensors (QuasAr1). The tractability of LiEp allows a versatile and precise alternative to state-of-the-art VGC drug screening platforms such as automated electrophysiology or FLIPR readers.
Highlights
Voltage-gated ion channels (VGCs) are frequently implicated in neural and cardiovascular disorders
We demonstrated the tractability and reproducibility of light-induced electrophysiology (LiEp) by exchanging optogenetic actuators and voltage sensors to optically investigate the activity of various VGCs
Our study focused on demonstrating the potential impact of optical drug screening rather than on new electrophysiological insights or novel drug evaluation
Summary
Voltage-gated ion channels (VGCs) are frequently implicated in neural and cardiovascular disorders. VGCs are challenging targets for drug screening since drug interaction is often confined to specific conformational channel states mediated by transient changes in the transmembrane potential. High-throughput optical in vitro assays were developed[10,11,12] They typically manipulate the transmembrane voltage or channel gating by non-physiological means, i.e. using artificial extracellular ion compositions or pharmacological agonists. The here introduced light-induced electrophysiology (LiEp) platform, as we named it, employs optogenetic “tandem” proteins[13] that enable contactless bi-directional control of the transmembrane potential by light They combine the blue-light actuated cation channel Channelrhodopsin-2 (ChR2)[14] with the yellow-light actuated ion pump ArchT15 as cell “depolarizer” and “hyperpolarizer”, respectively, in a single protein. Since hKv1.5 is expressed in the atria[20], drugs acting on hKv1.5 are devoid of the risk to induce ventricular arrhythmia[21]
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