title: DARPP-32, a dopamine-regulated neuronal phosphoprotein, is a potent inhibitor of protein phosphatase-1.
abstract: The neurotransmitter dopamine has been demonstrated by biochemical, histochemical and immunocytochemical techniques to be unevenly distributed in the mammalian central nervous system. DARPP-32 (dopamine- and cyclic-AMP-regulated phosphoprotein of molecular weight 32,000) is a neuronal phosphoprotein that displays a regional distribution in the mammalian brain very similar to that of dopamine-containing nerve terminals, being highly concentrated in the basal ganglia. The state of phosphorylation of DARPP-32 can be regulated by dopamine and by cyclic AMP in intact nerve cells, suggesting a role for this phosphoprotein in mediating certain of the effects of dopamine on dopaminoceptive cells. The observation that many of the physical and chemical properties of purified DARPP-32 resemble those of phosphatase inhibitor-1 (inhibitor-1), a widely distributed inhibitor of protein phosphatase-1, suggests that DARPP-32 might also function as a phosphatase inhibitor. We report here that DARPP-32 inhibits protein phosphatase-1 at nanomolar concentrations. Moreover, like inhibitor-1, DARPP-32 is effective as an inhibitor in its phosphorylated but not its dephosphorylated form. Thus, the basal ganglia of mammalian brain contain a region-specific neuronal phosphoprotein that is a protein phosphatase inhibitor.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D002148:Calmodulin-Binding Proteins; D002417:Cattle; D002421:Caudate Nucleus / Q000201:enzymology; D000242:Cyclic AMP / Q000502:physiology; D004298:Dopamine / Q000502:physiology*; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000502:physiology; D010750:Phosphoproteins / Q000378:metabolism / Q000494:pharmacology*; D054645:Protein Phosphatase 1
chemical_list: D002148:Calmodulin-Binding Proteins; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D000242:Cyclic AMP; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D002118:Calcium; D004298:Dopamine