An emerging role for kinase screening in GPCR drug discovery.

GPCRs are a large class of cell-surface receptors that are involved in a diverse array of biological processes, including many that are critical to diseases. As a result, GPCRs are a major focus for drug discovery research, and have been highly amenable to therapeutic intervention. However, the successes to date may represent the 'low-hanging fruit' (ie, outcomes that have been easiest to achieve). The signaling of many GPCRs is now recognized to be substantially more complex than initially thought. Thus, the traditional analysis of single GPCR-mediated secondary messengers for early-stage drug discovery, such as the measurement of Ca2+ or the formation of cAMP, may not provide all of the relevant signaling information on a target receptor or information on all of the effects of potential drugs. Given this complexity, the determination of other signaling events, such as the GPCR-mediated activation of major kinase pathways, including PI3K and MAPK, is likely to become increasingly important in the identification of indicators of GPCR function. Furthermore, the advent of highly efficient assays for detecting the GPCR-mediated activation of protein kinase targets allows this target class to be readily amenable to cell-based high-throughput screening programs.