Fluorescence-Based Functional Assays for Ca²⁺-Permeable ThermoTRP Channels

Transient receptor potential (TRP) ion channels are involved in a variety of fundamental physiological processes, and their malfunction produces numerous human diseases. Therefore, these proteins represent a class of attractive drug targets and a class of important off-targets for in vitro pharmacological profiling. In the past decades, the rapid progress in emerging functional assays and instrumentation has enabled to readily monitor thermoTRP channel activity, and to develop high throughput screening (HTS) assays for TPR drug discovery. Chronologically, functional methods for ion channels include the ligand binding assay, flux-based assay, electrophysiology, fluorescence-based assays, and, more recently, automated electrophysiological assays. Here we described the methodology used to monitor the functionality of two thermoTRPs, TRPV1 and TRPM8, based on Ca²⁺ microfluorography using a 96-well fluorescence plate reader that allows the implementation of a medium- to high-throughput format ideal for drug screening.