Ion channels are involved in various basic physiological processes, and their failure can lead to a variety of human diseases. Therefore, ion channels represent an attractive class of drug targets and an important class of off-target proteins, which can be used for in vitro pharmacological analysis. Over the past few decades, rapid advances in functional assays and instrument development have enabled high-throughput screening (HTS) activities in an ever-expanding list of channel types. In chronological order, HTS methods for ion channels include ligand binding assays, flux-based assays, fluorescence-based assays, and automated electrophysiological assays.
Ion channels are a very important family of membrane proteins involved in a variety of basic physiological processes. Their failure can cause a variety of human diseases. Traditionally, patch clamp electrophysiology has been the gold standard for ion channel research. However, this method is labor-intensive and low-throughput, and requires well-trained personnel to conduct experiments. Ion channels are targets that are difficult to study using high-throughput methods. Compared with other targets, the use of ion channels is hindered. Recently, rapid progress in the development of functional tests and instruments has enabled high throughput screening (HTS) activities on a growing list of channel types. Therefore, HTS aims to identify active compounds targeted by ion channels, which is of great interest to academic and industrial researchers.
In the past, the HTS method for ion channels has been widely developed and applied to most ion channels, including ligand binding assays, flux-based assays, fluorescence-based assays and automated electrophysiological assays. Patch clamp has been widely regarded as the gold standard for direct recording of ion channel activity. This technology can provide high-quality and physiologically relevant data of ion channel functions at the single cell or single channel (in a small piece of membrane) level. For pharmacological testing of compounds, it provides a standard for measuring the potency of the interaction between the compound and the channel. Although the conventional patch clamp provides a direct, information-rich real-time method to study channel functions, it has very low throughput and labor-intensive characteristics, which require skilled and well-trained personnel. In the past ten years, the development of automatic planar patch clamps has been a breakthrough. Many automated electrophysiological platforms have been developed.
High-throughput electrophysiology has many theoretical advantages and has broad prospects. The continuous development of existing platforms and new platforms for automated ion channel screening will keep up with the demand for ion channel safety analysis and ion channel targeted drug discovery.
Advances and improvements in ion channel HTS technology have accelerated the discovery of ion channel drugs. Fluorescent indicator dyes and a fluorescent plate reader (such as a fluorescent imaging plate reader (FLIPR Tetra)) can be used to detect ion flux signals. The electrophysiological method has the most direct method to measure ion channel activity and also provides flexibility for the analysis and optimization of each channel type. The combination of non-electrophysiological and electrophysiological HTS methods provides an integrated and cost-effective method for ion channel drug discovery and ensures high-quality data to be generated.
The development of ion channel screening technology has met most of the needs for drug discovery. Major instrument development work continues to improve the functionality of automated electrophysiological instruments, which are used in more ion channel types and cell types. Emerging trends focus on the exploration of reagents and the development of strategies that can be used in ion channel screening processes, including highly expressed ion channel stable cell lines, sensitive and specific indicators, and optimized screening strategies.
Drug discovery is a slow and complicated process. The identification of active ingredients is the first and crucial step for almost all drug targets. All work related to screening is moving towards the first step. Researchers may be interested in finding multiple chemical types of ion channel modulators (for example, normal modulators, allosteric modulators, or competitive antagonists).
Therefore, it is encouraged to adopt flexible strategy design to meet the needs of researchers, which greatly increases the probability of success. In addition, data analysis and management are also very important and critical in the HTS process, especially when analyzing large amounts of data across different detection methods and targets.
