Regulation of dopamine D-receptor activation in vivo by protein phosphatase 2B (calcineurin).
Mice lacking dopamine D2 receptors exhibit a significantly decreased agonist-promoted forebrain neocortical D1 receptor activation that occurs without changes in D1 receptor expression levels. This raises the possibility that, in brains of D2 mutants, a substantial portion of D1 receptors are uncoupled from their G protein, a phenomenon known as receptor desensitization. To test this, we examined D1-agonist-stimulated [35S]GTPgammaS binding (in the presence and absence of protein phosphatase inhibitors) and cAMP production (in the presence and absence of pertussis toxin) in forebrain neocortical tissues of wild-type mice and D2-receptor mutants. These studies revealed a decreased agonist-stimulated G-protein activation in D2 mutants. Moreover, whereas protein phosphatase 1/2A (PP1/2A) and 2B (PP2B) inhibitors decrease [35S]GTPgammaS binding in a concentration-dependent manner in wild type, they have either no (PP2B) or only partial (PP1/2A) effects in D2 mutants. Furthermore, for D2 mutants, immunoprecipitation experiments revealed increased basal and D1-agonist-stimulated phosphorylation of D1-receptor proteins at serine residues. Finally, D1 immunoprecipitates of both wild type and D2 mutants also contain protein kinase A (PKA) and PP2B immunoreactivities. In D2 mutants, however, the catalytic activity of the immunoprecipitated PP2B is abolished. These data indicate that neocortical D1 receptors are physically linked to PKA and PP2B and that the increased phosphorylation of D1 receptors in brains of D2 mutants is due to defective dephosphorylation of the receptor rather than increased kinase-mediated phosphorylation.
Division of Neuroscience, New York State Psychiatric Institute, New York, New York, USA.
Mella
M
Adlersberg
Shu-chi
SC
Hsiung
Sara B
SB
Glickstein
Kuo-peing
KP
Liu
Hadassah
H
Tamir
Claudia
C
Schmauss
D000262:Adenylyl Cyclases / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects / Q000235:genetics; D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D000242:Cyclic AMP / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018491:Dopamine Agonists / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism / Q000493:pharmacokinetics; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019579:Neocortex / Q000187:drug effects / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D010768:Phosphoserine / Q000032:analysis / Q000378:metabolism; D054645:Protein Phosphatase 1; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000172:deficiency / Q000235:genetics
D065095:Calcineurin Inhibitors; D018491:Dopamine Agonists; D004791:Enzyme Inhibitors; D046911:Macromolecular Substances; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D010768:Phosphoserine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; D019703:Calcineurin; D054645:Protein Phosphatase 1; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases