Receptor-mediated adenylyl cyclase activation through XLαs, the extra-large variant of the stimulatory G protein α-subunit

Abstract

XLαs, the large variant of the stimulatory G protein α subunit (Gsα), is derived from GNAS1 through the use of an alternative first exon and promoter. Gsα and XLαs have distinct amino-terminal domains, but are identical over the carboxyl-terminal portion encoded by exons 2-13. XLαs can mimic some functions of Gsα, including βγ interaction and adenylyl cyclase stimulation. However, previous attempts to demonstrate coupling of XLαs to typically Gs-coupled receptors have not been successful. We now report the generation of murine cell lines that carry homozygous disruption of Gnas exon 2, and are therefore null for endogenous XLαs and Gsα (GnasE2-/E2-). GnasE2-/E2- cells transfected with plasmids encoding XLαs and different heptahelical receptors, including the β2-adrenergic receptor and receptors for PTH, TSH, and CRF, showed agonist-mediated cAMP accumulation that was indistinguishable from that observed with cells transiently coexpressing Gsα and these receptors. Our findings thus indicate that XLαs is capable of functionally coupling to receptors that normally act via Gsα.