Phosphorylation and Inactivation of Protein Phosphatase 1 by Cyclin- Dependent Kinases

• Published in: Proceedings of the National Academy of Sciences - PNAS 1994-07, Vol.91 (14), p.6408-6412
• Main Authors: Dohadwala, Mariam, Edgar F. Da Cruz E Silva, Hall, Frederick L., Williams, Richard T., Carbonaro-Hall, Denise A., Nairn, Angus C., Greengard, Paul, Berndt, Norbert
• Format: Article
• Language: English
• Subjects: Amino acids; Amino Acids - analysis; Animals; Base Sequence; Biochemistry; Bone Neoplasms; CDC2 Protein Kinase - metabolism; Cell cycle; Cell Cycle - physiology; Cell Line; Cloning, Molecular; Cyclins; Cyclins - metabolism; Gels; Humans; Interphase; Kinetics; Mitosis; Molecular Sequence Data; Muscles - enzymology; Muscular system; Mutagenesis, Site-Directed; Oligodeoxyribonucleotides; Osteosarcoma; Peptide Mapping; Phosphatases; Phosphopeptides - chemistry; Phosphopeptides - isolation & purification; Phosphoprotein Phosphatases - antagonists & inhibitors; Phosphoprotein Phosphatases - isolation & purification; Phosphoprotein Phosphatases - metabolism; Phosphorylation; Protein isoforms; Protein Phosphatase 1; Protein Phosphatase 2; Proteins; Rabbits; Recombinant Proteins - antagonists & inhibitors; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Tumor Cells, Cultured
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.14.6408

Protein phosphatase 1 and protein phosphatase 2A contain potential phosphorylation sites for cyclin-dependent kinases. In the present study we found that rabbit skeletal muscle protein phosphatase 1, as well as recombinant protein phosphatase 1α and protein phosphatase 1γ 1, but not protein phosphatase 2A, was phosphorylated and inhibited by cdc2/cyclin A and cdc2/cyclin B. Phosphopeptide mapping and phospho amino acid analysis suggested that the phosphorylation site was located at a C-terminal threonine. Neither cdc2/cyclin A nor cdc2/cyclin B phosphorylated an active form of protein phosphatase 1α in which Thr-320 had been mutated to alanine, indicating that the phosphorylation occurred at this threonine residue. Furthermore, protein phosphatase 1, but not protein phosphatase 2A, activity was found to change during the cell cycle of human MG-63 osteosarcoma cells. The observed oscillations in protein phosphatase 1 activity during the cell cycle may be due, at least in part, to phosphorylation of protein phosphatase 1 by cyclin-dependent kinases. Together, the results suggest a mechanism for direct regulation of protein phosphatase 1 activity.