Functional coupling of a recombinant human 5-HT5A receptor to G-proteins in HEK-293 cells

1 We have cloned, expressed and pharmacologically characterized the Human 5-HT5A receptor. 2 We have shown that ligand activation of the Human 5-HT5A receptor results in functional coupling to G-proteins in HEK-293 cells. 3 Stimulation of the receptor with 5-CT (5-carboxamidotryptamine) resulted in a dose-dependent increase in the % [S-35]-GTP gamma S binding over the basal level. This is the first study to describe such G-protein activation for the Human 5-HT5A receptor in any cell. 4 A dose-dependent inhibition of cyclic AMP accumulation was observed in the recombinant Human 5-HT5A receptor cell line, suggesting a functional coupling to a G alpha i, G-protein in the HEK-293 cell line. 5 A ligand-stimulated reduction in the detectable level of the catalytic domain of protein kinase A (PKA) in nuclear extracts isolated from Human 5-HT5A expressing cells was observed. This observation was consistent with the reduction in the level of cyclic AMP accumulation, in response to receptor activation.