Multiplexed labeling of viable cells for high-throughput analysis of glycine receptor function using flow cytometry

Flow cytometry is an important drug discovery tool because it permits high-content multiparameter analysis of individual cells. A new method dramatically enhanced screening throughput by multiplexing many discrete fixed cell populations; however, this method is not suited to assays requiring functional cellular responses. HEK293 cells were transfected with unique mutant glycine receptors. Mutant receptor expression was confirmed by coexpression of yellow fluorescent protein (YFP). Commercially available cell-permeant dyes were used to label each glycine receptor expressing mutant with a unique optical code. All encoded cell lines were combined in a single tube and analyzed on a flow cytometer simultaneously before and after the addition of glycine receptor agonist. We decoded multiplexed cells that expressed functionally distinct glycine receptor chloride channels and analyzed responses to glycine in terms of chloride-sensitive YFP expression. Here, data provided by flow cytometry can be used to discriminate between functional and nonfunctional mutations in the glycine receptor, a process accelerated by the use of multiplexing. Further, this data correlates to data generated using a microscopy-based technique. The present study demonstrates multiplexed labeling of live cells, to enable cell populations to be subject to further cell culture and experimentation, and compares the results with those obtained using live cell microscopy.