Signaling pathways leading to phosphorylation of Akt and GSK-3β by activation of cloned human and rat cerebral D₂and D₃ receptors.
Although dopamine (DA) regulates the serine/threonine kinase Akt and its downstream substrate glycogen synthase kinase-3β (GSK-3β), the direct influence of dopaminergic receptors remains poorly characterized. Short-term incubation of Chinese hamster ovary (CHO)-expressed human (h)D(₂L) and hD₃) receptors with DA (maximal effect, 5-10 min) phosphorylated Akt (Thr308 and Ser473) and GSK-3β (Ser9), actions blocked by the selective D₂ and D₃ antagonists, 3-[4-(4-chlorophenyl)-4-hydroxypiperidin-l-yl]methyl-1H-indole (L741,626) and (3aR,9bS)-N[4-(8-cyano-1,3a,4,9b-tetrahydro-3H-benzopyrano[3,4-c]pyrrole-2-yl)-butyl] (4-phenyl)benzamide (S33084), respectively. Similar findings were acquired with the specific D₂/D₃ receptor agonist quinelorane, which also enhanced (10 min after administration) levels of p-Akt and p-GSK-3β in rat nucleus accumbens, an action blocked by the D₂/D₃ receptor antagonist raclopride. Akt and GSK-3β phosphorylation mediated via CHO-expressed hD(₂L) and hD₃ receptors was prevented by pertussis toxin and by inhibitors of insulin-like growth factor-1 receptors as well as phosphatidylinositol 3-kinase and Src. Likewise, chelation of intracellular Ca²+ and interference with an "atypical" phorbol ester-insensitive protein kinase C (PKC) abolished recruitment of Akt and GSK-3β. Inactivation of PKCμ blocked Akt and GSK-3β phosphorylation at hD(₂L) receptors. However, blockade of conventional PKC isoforms attenuated the actions of DA at hD₃ receptors only. Furthermore, phospholipase C (PLC), calmodulin, and Akt inhibitors abolished DA-induced GSK-3β phosphorylation by hD₃ receptors, whereas phosphorylation by hD(₂L) receptors partially involved calmodulin, Akt, and extracellular signal-regulated kinase (ERK) 1/2. In conclusion, at both hD(₂L) and hD₃ receptors, DA elicited a G(i/o)- and Ca²+/calmodulin-dependent phosphorylation of Akt and GSK-3β via transactivation of insulin-like growth factor 1 receptor. However, significant differences were seen regarding the involvement of PLC, calmodulin, and ERK1/2.
Institut de Recherches Servier, Psychopharmacology Department, 125 Chemin de Ronde, 78290 Croissy sur Seine, France. clotilde.mannourylacour@fr.netgrs.com
Clotilde
C
Mannoury la Cour
Marie-Josèphe
MJ
Salles
Valérie
V
Pasteau
Mark J
MJ
Millan
D000818:Animals; D016466:CHO Cells; D002540:Cerebral Cortex / Q000378:metabolism*; D003001:Cloning, Molecular / Q000379:methods; D006224:Cricetinae; D003412:Cricetulus; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D008297:Male; D010766:Phosphorylation / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2 / Q000235:genetics / Q000378:metabolism*; D050637:Receptors, Dopamine D3 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; C113776:dopamine D2L receptor; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3