G protein-coupled receptor (GPCR) has been the primary therapeutic targets for many diseases. Agonists and antagonists of various GPCR are estimated to occupy approximately 35% of the drug market (1). Extracellular signals perceived by GPCR are transmitted via G proteins and trigger intracellular signaling cascades resulting in a plethora of physiological responses. G proteins usually are categorized into four main classical subfamilies according to their α subunits: Gαq/11, Gαs, Gαi/o, Gα12/13 (2). Main subunits Gαq/11, Gαs, Gαi/o and G12/13 are commonly thought to be coupled with phospholipase C (PLC), adenylyl cyclase activation, adenylyl cyclase inactivation, and other small GTPase families, respectively (3). Gαq/11 activates phospholipase Cβ pathway leading to intracellular Ca 2+ mobilization. Gαs and Gαi/o proteins regulate adenylyl cyclase activation and inhibition, respectively, which control intracellular cAMP level. Thus, G proteins are important signal transducing molecules for various cellular responses. Malfunction of GPCR signaling pathways are involved in many diseases, such as diabetes, cardiovascular diseases, and certain forms of cancers (4).