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 Hu man 5-HT5A receptor. 2 We have shown that ligand activation of the Hum an 5-HT5A receptor results in functional coupling to G-proteins in HEK -293 cells. 3 Stimulation of the receptor with 5-CT (5-carboxamidotryp tamine) resulted in a dose-dependent increase in the % [S-35]-GTP gamm a 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 i n the recombinant Human 5-HT5A receptor cell line, suggesting a functi onal 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 d omain of protein kinase A (PKA) in nuclear extracts isolated from Huma n 5-HT5A expressing cells was observed. This observation was consisten t with the reduction in the level of cyclic AMP accumulation, in respo nse to receptor activation.