COUPLING OF HUMAN D-1 DOPAMINE-RECEPTORS TO DIFFERENT GUANINE-NUCLEOTIDE-BINDING PROTEINS - EVIDENCE THAT D-1 DOPAMINE-RECEPTORS CAN COUPLETO BOTH G(S) AND G(O)

Coupling between D-1 dopamine receptors and G proteins in cell lines e xpressing human D-1 receptors and different G proteins was examined. P ertussis toxin (PTX) treatment of rat pituitary GH(4)C(1) cells signif icantly reduced, but did not abolish, agonist high affinity binding si tes of the D-1 dopamine receptor; in SK-N-MC neuroblastoma cells, PTX failed to have any effect on D-1 high affinity sites. Cholera toxin (C TX) treatment of GH(4)C(1) cells reduced but did not abolish the high affinity sites of D-1 receptors, while in SK-N-MC cells, treatment wit h CTX abolished all the high affinity sites. Western blot analyses wit h specific antisera indicated that G(s) alpha, Q(i1)alpha, G(i3)alpha and G(q) alpha were expressed in both cell lines, while G(i2)alpha and G(o) alpha were expressed in GH(4)C(1) but not SK-N-MC cells. Antiser a NEI-805 (anti-G(s) alpha) and 9072 (anti-G(o) alpha) immunoprecipita ted 24 +/- 4.3 and 34.4 +/- 6.9%, respectively, of G protein-associate d D-1 dopamine receptors. Antisera 3646 (anti-G(i1)alpha), 1521 (anti- G(i2)alpha), 1518 (anti-G(i3)alpha), and 0941 (anti-G(q) alpha) failed to coimmunoprecipitate appreciable levels df soluble receptors. These data indicate that D-1 dopamine receptors are coupled to both G(s) al pha and G(o) alpha but not to G(q) alpha.