Multiple signaling routes involved in the regulation of adenylyl cyclase and extracellular regulated kinase by dopamine D(2) and D(3) receptors.
Most G protein coupled receptors (GPCR) regulate multiple cellular processes by coupling to more than one kind of G protein. Furthermore, recent studies have reported G protein-independent/β-arrestin-dependent signaling pathway for some GPCRs. Dopamine D(2) and D(3) receptors (D(2)R, D(3)R), the major targets of currently used antipsychotic drugs, are co-expressed in some of the same dopaminergic neurons and regulate the same overlapping effectors. However, the specific subunits of G proteins that regulate each signaling pathway are not clearly identified. In addition, the existence of β-arrestin-dependent/G protein-independent signaling is not clear for these receptors. In this study, we determined the G protein subtypes and β-arrestin dependency involved in the signaling of D(2)R and D(3)R, which was measured by inhibition of adenylyl cyclase and extracellular signal-regulated kinase (ERK) activation. For the inhibition of cAMP production in HEK-293 cells, D(2)R used the Gαo subunit but D(3)R used the βγ subunit of Gi family proteins. For the regulation of ERK activation, D(2)R used the α subunits of Gi/o proteins both in HEK-293 cells and COS-7 cells, but D(3)R used Gαo and Gβγ in HEK-293 cells and COS-7 cells, respectively. β-Arrestin-dependent/G protein-independent ERK activation was not observed for both D(2)R and D(3)R. Agonist-induced β-arrestin translocation was observed with D(2)R but not with D(3)R, and β-arrestins exerted inhibitory influences on G protein-dependent ERK activation by D(2)R, but not D(3)R. These results show that the D(2)R and D(3)R, which have overlapping cellular expressions and functional roles, employ distinct G protein subunits depending on the cell types and the effectors they control.
Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea.
Mingli
M
Jin
Chengchun
C
Min
Mei
M
Zheng
Dong-Im
DI
Cho
Soo-Jin
SJ
Cheong
Hitosh
H
Kurose
Kyeong-Man
KM
Kim
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D019390:Arrestins / Q000378:metabolism; D019556:COS Cells; D002522:Chlorocebus aethiops; D000242:Cyclic AMP / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D021122:Protein Subunits / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D050637:Receptors, Dopamine D3 / Q000378:metabolism*; D015398:Signal Transduction; D000071557:beta-Arrestins
D019390:Arrestins; D021122:Protein Subunits; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D000071557:beta-Arrestins; D000242:Cyclic AMP; D048049:Extracellular Signal-Regulated MAP Kinases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases