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

Abstract

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 proteins. Given that different GPCRs can discriminate against distinct G proteins, a universal G protein adapter is extremely desirable. In this report, the authors evaluated two highly promiscuous Gα_16/z chimeras, 16z25 and 16z44, for their ability to translate GPCR activation into Ca²⁺ mobilization using the fluorescence imaging plate reader (FLIPR) and aequorin. A panel of 24 G_s- or G_i-coupled receptors was examined for their functional association with the Gα_16/z chimeras. Although most of the GPCRs tested were incapable of inducing Ca²⁺ 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 Gα₁₆ to mobilize intracellular Ca²⁺. Analysis of dose-response curves obtained with the δ-opioid, dopamine D₁ , and Xenopus melatonin Mel1c receptors revealed that the Gα _16/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 ²⁺ mobilization. (Journal of Biomolecular Screening 2003:39-49)