Dopamine D2 Receptor-Mediated Heterologous Sensitization of AC5 Requires Signalosome Assembly

Chronic dopamine receptor activation is implicated in several central nervous system disorders. Although acute activation of Gα(i)-coupled D(2) dopamine receptors inhibits adenylyl cyclase, persistent activation enhances adenylyl cyclase activity, a phenomenon called heterologous sensitization. Previous work revealed a requirement for Gα(s) in D(2)-induced heterologous sensitization of AC5. To elucidate the mechanism of Gα(s) dependency, we expressed Gα(s) mutants in Gα(s)-deficient Gnas(E2-/E2-) cells. Neither Gα(s)-palmitoylation nor Gα(s)-Gβγ interactions were required for sensitization of AC5. Moreover, we found that coexpressing βARKct-CD8 or Sar1(H79G) blocked heterologous sensitization. These studies are consistent with a role for Gα(s)-AC5 interactions in sensitization however, Gβγ appears to have an indirect role in heterologous sensitization of AC5, possibly by promoting proper signalosome assembly.