Sutherland C, Leighton I A, Cohen P
Department of Biochemistry, University of Dundee, Scotland, U.K.
Biochem J. 1993 Nov 15;296 ( Pt 1)(Pt 1):15-9. doi: 10.1042/bj2960015.
The beta-isoform of glycogen synthase kinase-3 (GSK3 beta) isolated from rabbit skeletal muscle was inactivated 90-95% following incubation with MgATP and either MAP kinase-activated protein kinase-1 (MAPKAP kinase-1, also termed RSK-2) or p70 S6 kinase (p70S6K), and re-activated with protein phosphatase 2A. MAPKAP kinase-1 and p70S6K phosphorylated the same tryptic peptide on GSK3 beta, and the site of phosphorylation was identified as the serine located nine residues from the N-terminus of the protein. The inhibitory effect of Ser-9 phosphorylation on GSK3 beta activity was observed with three substrates, (inhibitor-2, c-jun and a synthetic peptide), and also with glycogen synthase provided that 0.15 M KCl was added to the assays. The results suggest that Ser-9 phosphorylation underlies the reported inhibition of GSK3 beta by insulin and that GSK3 may represent a point of convergence of two major growth-factor-stimulated protein kinase cascades.
从兔骨骼肌中分离出的糖原合酶激酶-3的β亚型（GSK3β），在与MgATP以及丝裂原活化蛋白激酶激活的蛋白激酶-1（MAPKAP激酶-1，也称为RSK-2）或p70核糖体蛋白S6激酶（p70S6K）一起孵育后，其活性被抑制了90%-95%，随后用蛋白磷酸酶2A重新激活。MAPKAP激酶-1和p70S6K使GSK3β上的同一条胰蛋白酶肽段发生磷酸化，磷酸化位点被确定为该蛋白N端起第九个残基处的丝氨酸。在三种底物（抑制剂-2、c-jun和一种合成肽）上均观察到丝氨酸9磷酸化对GSK3β活性的抑制作用，并且在测定中加入0.15M KCl的情况下，对糖原合酶也有此作用。结果表明，丝氨酸9磷酸化是胰岛素对GSK3β抑制作用的基础，并且GSK3可能代表了两条主要的生长因子刺激的蛋白激酶级联反应的汇聚点。
