Demonstration of the dynamic mass redistribution label-free technology as a useful cell-based pharmacological assay for endogenously expressed GABAA receptors

Abstract

Within the continuous quest for the discovery of pharmacologically interesting compounds, the development of new and superior drug screening assays is desired. In recent years, the use of label-free techniques has paved the way for an alternative high-throughput screening method. An example is the Epic® optical-based biosensor that relies on dynamic mass redistribution (DMR) for detection. So far, DMR assays have been mostly used to study G protein-coupled receptor (GPCR) pharmacology. Here, we demonstrate the utility of this assay for investigating ligand-gated ion channel receptors. Using the immortalized IMR-32 neuroblastoma cell line, which expresses relatively high levels of several endogenous GABAA receptor subunits, we show that GABA produces concentration-dependent cellular responses that can be measured and quantified in real-time. With the aid of the GABAA receptor-specific agonist muscimol and the selective antagonists gabazine and bicuculline, we confirm that the data corresponds to that of a GABAA receptor. Based on quantitative real-time PCR measurements, the subunits α3, α5, β3 and θ are the most likely candidates for integration into functional receptors. Our demonstration that label-free methods such as the Epic technology can be used to characterize endogenous GABAA receptors in the IMR-32 cell line is exemplary for the superfamily of ligand-gated ion channel receptors, and holds interesting perspectives in relation to identifying novel mechanisms of action.