Stimulation of increases in intracellular calcium and prostaglandin E2 generation in chinese hamster ovary cells expressing receptor Gα16 fusion proteins

We examined whether fusion proteins of G protein-coupled receptors with the a subunit of G(16) (Galpha(16)) could activate downstream signals. We expressed fusion proteins of G(i)-coupled receptors, i.e. CX3C chemokine receptor 1 (CX(3)CR1) and M-2 receptor, in Chinese hamster ovary cells. An agonist for CX3CR1 induced greater increases in intracellular Ca2+ and prostaglandin E-2 generation in cells expressing CX3CR1-Galpha(16) fusion protein than in cells expressing CX(3)CR1 alone or both CX(3)CR1 and Galpha(16) separately. Similarly, agonist-induced prostaglandin E-2 generation was greater in cells expressing M-2-Galpha(16) fusion protein than ones expressing M-2 alone or both M-2 and Galpha(16) separately. In cells expressing fusion proteins with Galpha(16) of G(q)-coupled receptors, i.e. urotensin II receptor and M-1 receptor, the relevant agonists induced similar increases in intracellular Ca2+ and prostaglandin E-2 generation as in ones expressing the receptor alone. In cells expressing urotensin II receptor-Galpha(16) fusion protein, prostaglandin E-2 generation exhibited a lower EC50 value than the intracellular Ca2+ increase. These results indicate that agonist-stimulated receptor-Galpha(16) fusion proteins are coupled to downstream signaling pathways, and suggest that receptor-Galpha(16) fusion proteins may be useful for screening for ligands of orphan G protein-coupled receptors and G(i)-coupled receptors.