The influence of G protein subtype on agonist action at D 2 dopamine receptors

Abstract

In previous studies, we have shown that agonists influence the ability of D 2 dopamine receptors to couple to G proteins and here we extend this work. The human D 2Short dopamine receptor and a natural polymorphism of this D 2Short(Ser 311Cys), have been studied by co-expressing the receptors in insect cells with Gβ 1γ 2 and either Gα o, Gα i1, Gα i2 or Gα i3 G protein subunits. These preparations have been used to study the G protein coupling profiles of the two receptors and the influence of agonists. Receptor/G protein coupling was analysed in dopamine/[ 3H]spiperone competition binding experiments and through stimulation of [ 35S]GTPγS binding. Although the Ser 311Cys polymorphism itself had no appreciable effect on the G protein coupling specificity of the D 2 receptor, agonist stimulation of [ 35S]GTPγS binding, revealed that both dopamine and (+)-3PPP showed a clear preference for Gα o compared to the Gα i subtypes, but quinpirole did not. These results indicate that agonists are able to stabilise different receptor conformations with different abilities to couple to G proteins.