Kobayashi T, Kusuda K, Ohnishi M, Wang H, Ikeda S, Hanada M, Yanagawa Y, Tamura S
Department of Biochemistry, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
FEBS Lett. 1998 Jul 3;430(3):222-6. doi: 10.1016/s0014-5793(98)00604-8.
Of the six distinct isoforms of mouse protein phosphatase 2C (PP2C) (alpha, beta-1, beta-2, beta-3, beta-4 and beta-5), PP2C alpha was specifically phosphorylated on the serine residue(s) when expressed in COS7 cells. Analysis of phosphorylation sites using site-directed mutagenesis demonstrated that Ser-375 and/or Ser-377 were phosphorylated in vivo. These serine residues were the sites of phosphorylation by casein kinase II in vitro. Phosphorylation of PP2C alpha was enhanced two-fold by the addition of okadaic acid to the culture medium, but addition of cyclosporin A had no such effect. These results suggest that the expressed PP2C alpha is phosphorylated by a casein kinase II-like protein kinase and dephosphorylated by PP1 and/or PP2A in COS7 cells.
在小鼠蛋白磷酸酶2C（PP2C）的六种不同亚型（α、β-1、β-2、β-3、β-4和β-5）中，PP2Cα在COS7细胞中表达时，其丝氨酸残基会发生特异性磷酸化。使用定点诱变分析磷酸化位点表明，Ser-375和/或Ser-377在体内被磷酸化。这些丝氨酸残基是酪蛋白激酶II在体外的磷酸化位点。向培养基中添加冈田酸可使PP2Cα的磷酸化增强两倍，但添加环孢菌素A则没有这种效果。这些结果表明，在COS7细胞中，表达的PP2Cα被一种类似酪蛋白激酶II的蛋白激酶磷酸化，并被PP1和/或PP2A去磷酸化。
