A cell-based PDE4 assay in 1536-well plate format for high-throughput screening

The cyclic nucleotide phosphodiesterases (PDEs) are intracellular enzymes that catalyze the hydrolysis of 3,'5'-cyclic nucleotides, such as cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), to their corresponding 5'nucleotide monophosphates. These enzymes play an important role in controlling cellular concentrations of cyclic nucleotides and thus regulate a variety of cellular signaling events. PDEs are emerging as drug targets for several diseases, including asthma, cardiovascular disease, attention-deficit hyperactivity disorder, Parkinson's disease, and Alzheimer's disease. Although biochemical assays with purified recombinant PDE enzymes and cAMP or cGMP substrate are commonly used for compound screening, cell-based assays would provide a better assessment of compound activity in a more physiological context. The authors report the development and validation of a new cell-based PDE4 assay using a constitutively active G-protein-coupled receptor as a driving force for cAMP production and a cyclic nucleotide-gated cation channel as a biosensor in 1536-well plates.