[7] Functional assays to study coupling of dopamine D2 receptors to G proteins

Publisher Summary This chapter discusses the methods used to study the coupling of the D2 dopamine receptors to the G proteins. These studies allow to show that D2L couples preferentially to the α subunit of G i2 in the inhibition of adenylatecyclase. The results obtained with this method are reproducible and afford the advantage of studying receptor/G protein coupling in different types of cells. Considering that, each cell type contains its own combination of specific G proteins; many cell types, tested in order to get a complete picture of the signal transduction pathway utilized by each receptor. Performing these studies through the establishment of stable cell lines, although perhaps useful for some cases, is a long and time-consuming approach. In addition, the comparison of subtypes of the same receptor requires the establishment of cells expressing the same amounts of the receptors. The transcriptional assay has the advantage of amplifying the response to the activation of membrane receptors and enabling study of their effect at the transcriptional level. This method is rapid and easy to perform. The combined use of the techniques perhaps helps to characterize the interactions of membrane receptors with members of the G protein family and to obtain insights in the complexity of signal transduction mechanisms mediated by the 7TM domain G-protein-coupled receptors.