Phosphorylation of DARPP-32 by Cdk5 modulates dopamine signalling in neurons.
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.
Bibb
J A
JA
Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10021, USA.
Snyder
G L
GL
Nishi
A
A
Yan
Z
Z
Meijer
L
L
Fienberg
A A
AA
Tsai
L H
LH
Kwon
Y T
YT
Girault
J A
JA
Czernik
A J
AJ
Huganir
R L
RL
Hemmings
H C
HC
Nairn
A C
AC
Greengard
P
P
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
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