Dopamine- and cAMP-regulated phosphoprotein DARPP-32: phosphorylation of Ser-137 by casein kinase I inhibits dephosphorylation of Thr-34 by calcineurin.
Although protein phosphatases appear to be highly controlled in intact cells, relatively little is known about the physiological regulation of their activity. DARPP-32, a dopamine- and cAMP-regulated phosphoprotein of apparent M(r) 32,000, is phosphorylated in vitro by casein kinase I, casein kinase II, and cAMP-dependent protein kinase on sites phosphorylated in vivo. DARPP-32 phosphorylated on Thr-34 by cAMP-dependent protein kinase is a potent inhibitor of protein phosphatase 1 and an excellent substrate for calcineurin, a Ca2+/calmodulin-dependent protein phosphatase. Here we provide evidence, using both purified proteins and brain slices, that phosphorylation of DARPP-32 on Ser-137 by casein kinase I inhibits the dephosphorylation of Thr-34 by calcineurin. This inhibition occurs only when phospho-Ser-137 and phospho-Thr-34 are located on the same DARPP-32 molecule and is not dependent on the mode of activation of calcineurin. The results demonstrate that the inhibition is due to a modification in the properties of the substrate which alters its dephosphorylation rate. Thus, casein kinase I may play a physiological role in striatonigral neurons as a modulator of the regulation of protein phosphatase 1 via DARPP-32.
Desdouits
F
F
Institut National de la Santé et de la Recherche Médicale U114, Collège de France, Paris.
Siciliano
J C
JC
Greengard
P
P
Girault
J A
JA
D000595:Amino Acid Sequence; D000818:Animals; D019703:Calcineurin; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D002148:Calmodulin-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047388:Casein Kinases; D002417:Cattle; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D011494:Protein Kinases / Q000378:metabolism*; D054645:Protein Phosphatase 1; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine; D013378:Substantia Nigra / Q000378:metabolism; D013912:Threonine; D013950:Thymus Gland / Q000201:enzymology
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D013912:Threonine; D008345:Manganese; D012694:Serine; D000242:Cyclic AMP; D011494:Protein Kinases; D047388:Casein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D002118:Calcium; D004298:Dopamine