Gα 16/z Chimeras Efficiently Link a Wide Range of G Protein— Coupled Receptors to Calcium Mobilization

G protein-coupled receptors (GPCRs) represent a class of important therapeutic targets for drug discovery. The integration of GPCRs into contemporary high-throughput functional assays is critically dependent on the presence of appropriate G pro- teins. Given that different GPCRs can discriminate against distinct G proteins, a universal G protein adapter is extremely de- sirable. In this report, the authors evaluated two highly promiscuous Gα16/z chimeras, 16z25 and 16z44, for their ability to translate GPCR activation into Ca 2+ mobilization using the fluorescence imaging plate reader (FLIPR) and aequorin. A panel of 24 G s -o r G i-coupled receptors was examined for their functional association with the Gα16/z chimeras. Although most of the GPCRs tested were incapable of inducing Ca 2+ mobilization upon their activation by specific agonists, the introduction of 16z25 or 16z44 allowed all of these GPCRs to mediate agonist-induced Ca 2+ mobilization. In contrast, only 16 of the GPCRs tested were capable of using Gα 16 to mobilize intracellular Ca 2+ . Analysis of dose-response curves obtained with the δ-opioid, dopamine D 1, and Xenopus melatonin Mel1c receptors revealed that the Gα16/z chimeras possess better sensitivity than Gα16 in both the FLIPR and aequorin assays. Collectively, these studies help to validate the promiscuity of the Gα 16/z chimeras as well as their application in contemporary drug-screening assays that are based on ligand-induced Ca