A G protein-biased designer G protein-coupled receptor useful for studying the physiological relevance of G_q/11-dependent signaling pathways

Designer receptors exclusively activated by a designer drug (DREADDs) are clozapine-N-oxide-sensitive designer G protein-coupled receptors (GPCRs) that have emerged as powerful novel chemogenetic tools to study the physiological relevance of GPCR signaling pathways in specific cell types or tissues. Like endogenous GPCRs, clozapine-N-oxide-activated DREADDs do not only activate heterotrimeric G proteins but can also trigger β-arrestin-dependent (G protein-independent) signaling. To dissect the relative physiological relevance of G protein-mediated versus β-arrestin-mediated signaling in different cell types or physiological processes, the availability of G proteinand β-arrestin-biased DREADDs would be highly desirable. In this study, we report the development of a mutationally modified version of a non-biased DREADD derived from the M³muscarinic receptor that can activate G_q/11 with high efficacy but lacks the ability to interact with β-arrestins. We also demonstrate that this novel DREADD is active in vivo and that cell type-selective expression of this new designer receptor can provide novel insights into the physiological roles of G protein (G_q/11)-dependent versus β-arrestin-dependent signaling in hepatocytes. Thus, this novel G_q/11-biased DREADD represents a powerful new tool to study the physiological relevance of G_q/11-dependent signaling in distinct tissues and cell types, in the absence of β-arrestin-mediated cellular effects. Such studies should guide the development of novel classes of functionally biased ligands that show high efficacy in various pathophysiological conditions but display a reduced incidence of side effects.