Dohadwala M, da Cruz e Silva E F, Hall F L, Williams R T, Carbonaro-Hall D A, Nairn A C, Greengard P, Berndt N
Department of Pediatrics, Childrens Hospital Los Angeles, University of Southern California 90027.
Proc Natl Acad Sci U S A. 1994 Jul 5;91(14):6408-12. 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 1 alpha and protein phosphatase 1 gamma 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 1 alpha 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.
蛋白磷酸酶1和蛋白磷酸酶2A含有细胞周期蛋白依赖性激酶的潜在磷酸化位点。在本研究中，我们发现兔骨骼肌蛋白磷酸酶1以及重组蛋白磷酸酶1α和蛋白磷酸酶1γ1可被cdc2/细胞周期蛋白A和cdc2/细胞周期蛋白B磷酸化并受到抑制，但蛋白磷酸酶2A则不然。磷酸肽图谱分析和磷酸氨基酸分析表明，磷酸化位点位于C末端的苏氨酸。cdc2/细胞周期蛋白A和cdc2/细胞周期蛋白B均未使Thr-320已突变为丙氨酸的活性形式的蛋白磷酸酶1α磷酸化，这表明磷酸化发生在该苏氨酸残基上。此外，发现在人MG-63骨肉瘤细胞的细胞周期中，蛋白磷酸酶1的活性发生变化，而蛋白磷酸酶2A的活性则未发生变化。在细胞周期中观察到的蛋白磷酸酶1活性的振荡可能至少部分归因于细胞周期蛋白依赖性激酶对蛋白磷酸酶1的磷酸化作用。这些结果共同提示了一种直接调节蛋白磷酸酶1活性的机制。
