CONTROL OF YEAST MATING SIGNAL TRANSDUCTION BY A MAMMALIAN BETA-2-ADRENERGIC RECEPTOR AND GS ALPHA-SUBUNIT

To facilitate functional and mechanistic studies of receptor-G protein interactions by expression of the human β2-adrenergic receptor (hβ-AR) has been expressed in Saccharomyces cerevisiae. This was achieved by placing a modified hβ-AR gene under control of the galactose-inducible GAL1 promoter. After induction by galactose, functional hβ-AR was expressed at a concentration several hundred times as great as that found in any human tissue. As determined from competitive ligand binding experiments, hβ-AR expressed in yeast displayed characteristic affinities, specificity, and stereoselectivity. Partial activation of the yeast pheromone response pathway by β-adrenergic receptor agonists was achieved in cells coexpressing hβ-AR and a mammalian G protein (Gs) α subunit-demonstrating that these components can couple to each other and to downstream effectors when expressed in yeast. This in vivo reconstitution system provides a new approach for examining ligand binding and G protein coupling to cell surface receptors.