title: Phosphorylation of DARPP-32 by Cdk5 modulates dopamine signalling in neurons.
abstract: The physiological state of the cell is controlled by signal transduction mechanisms which regulate the balance between protein kinase and protein phosphatase activities. Here we report that a single protein can, depending on which particular amino-acid residue is phosphorylated, function either as a kinase or phosphatase inhibitor. DARPP-32 (dopamine and cyclic AMP-regulated phospho-protein, relative molecular mass 32,000) is converted into an inhibitor of protein phosphatase 1 when it is phosphorylated by protein kinase A (PKA) at threonine 34. We find that DARPP-32 is converted into an inhibitor of PKA when phosphorylated at threonine 75 by cyclin-dependent kinase 5 (Cdk5). Cdk5 phosphorylates DARPP-32 in vitro and in intact brain cells. Phospho-Thr 75 DARPP-32 inhibits PKA in vitro by a competitive mechanism. Decreasing phospho-Thr 75 DARPP-32 in striatal slices, either by a Cdk5-specific inhibitor or by using genetically altered mice, results in increased dopamine-induced phosphorylation of PKA substrates and augmented peak voltage-gated calcium currents. Thus DARPP-32 is a bifunctional signal transduction molecule which, by distinct mechanisms, controls a serine/threonine kinase and a serine/threonine phosphatase.
authors.affiliation: Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10021, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Bibb
authors.forename: G L
authors.initials: GL
authors.lastname: Snyder
authors.forename: A
authors.initials: A
authors.lastname: Nishi
authors.forename: Z
authors.initials: Z
authors.lastname: Yan
authors.forename: L
authors.initials: L
authors.lastname: Meijer
authors.forename: A A
authors.initials: AA
authors.lastname: Fienberg
authors.forename: L H
authors.initials: LH
authors.lastname: Tsai
authors.forename: Y T
authors.initials: YT
authors.lastname: Kwon
authors.forename: J A
authors.initials: JA
authors.lastname: Girault
authors.forename: A J
authors.initials: AJ
authors.lastname: Czernik
authors.forename: R L
authors.initials: RL
authors.lastname: Huganir
authors.forename: H C
authors.initials: HC
authors.lastname: Hemmings
authors.forename: A C
authors.initials: AC
authors.lastname: Nairn
authors.forename: P
authors.initials: P
authors.lastname: Greengard
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism; D066298:In Vitro Techniques; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000201:enzymology / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013912:Threonine / Q000378:metabolism
chemical_list: D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D004791:Enzyme Inhibitors; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D013912:Threonine; D051360:Cyclin-Dependent Kinase 5; D017868:Cyclic AMP-Dependent Protein Kinases; D016203:CDC2 Protein Kinase; C495906:Cdk5 protein, mouse; D018844:Cyclin-Dependent Kinases; D004298:Dopamine