Roles of G protein and beta-arrestin in dopamine D2 receptor-mediated ERK activation.

ERK activation by dopamine D(2) receptor (D(2)R) has been extensively characterized in various cell types including brain tissues. However, the involvement of beta-arrestin in the D(2)R-mediated ERK activation is not clear yet. Three different strategies were employed in this study to determine the roles of G protein or beta-arrestin in D(2)R-mediated ERK activation. The cellular level of beta-arrestins was reduced by RNA interference and pertussis toxin-insensitive Gi proteins were used to identify the G protein involved. Finally point mutations of D(2)R in which coupling with G protein was abolished but the interaction with beta-arrestin was increased, were employed to determine whether the affinity between D(2)R and beta-arrestin is a critical factor for beta-arrestin-mediated ERK activation. Our results show that G(i2) protein is involved in D(2)R-mediated ERK activation but beta-arrestins are either not involved or play minor role.