Characterization of the interaction between DARPP-32 and protein phosphatase 1 (PP-1): DARPP-32 peptides antagonize the interaction of PP-1 with binding proteins.
The catalytic subunit of PP-1 (PP-1C) is potently inhibited (IC50, approximately 1 nM) by DARPP-32 (dopamine- and cAMP-regulated phosphoprotein, M(r) 32,000), inhibitor-1, and inhibitor-2. The NH2-terminal 50 amino acid residues of DARPP-32 and inhibitor-1 are similar, and phosphorylation of a common threonine residue (Thr-34/Thr-35) is necessary for inhibition of PP-1C. We have characterized further the interaction between DARPP-32 and PP-1C. Using synthetic peptides derived from the NH2-terminal region of DARPP-32, residues 6-11, RKKIQF, have been shown to be required for inhibition of PP-1C. Peptides containing this motif were able to antagonize the inhibition of PP-1C by phospho-DARPP-32 and phosphoinhibitor-1. The inhibition of PP-1C by inhibitor-2, but not by okadaic acid, microcystin, or calyculin A, was also attentuated by these antagonist peptides. These results together with results from other studies support a model in which two subdomains of phospho-DARPP-32 interact with PP-1C. The region encompassing phospho-Thr-34 appears to interact with the active site of the enzyme blocking enzyme activity. The region encompassing the RKKIQF motif binds to a domain of PP-1C removed from the active site. Amino acid sequence analysis indicates that basic and hydrophobic features of the RKKIQF motif are conserved in the binding domains of certain PP-1C targeting proteins, suggesting that interaction of inhibitor proteins and targeting proteins may be mutually exclusive.
Kwon
Y G
YG
Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, NY 10021, USA.
Huang
H B
HB
Desdouits
F
F
Girault
J A
JA
Greengard
P
P
Nairn
A C
AC
D000595:Amino Acid Sequence; D000818:Animals; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010750:Phosphoproteins; D011485:Protein Binding; D054645:Protein Phosphatase 1; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D004791:Enzyme Inhibitors; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1