Cross D A, Alessi D R, Vandenheede J R, McDowell H E, Hundal H S, Cohen P
Department of Biochemistry, University of Dundee, Scotland, UK.
Biochem J. 1994 Oct 1;303 ( Pt 1)(Pt 1):21-6. doi: 10.1042/bj3030021.
Glycogen synthase kinase-3 (GSK3) is inactivated in vitro by p70 S6 kinase or MAP kinase-activated protein kinase-1 beta (MAPKAP kinase-1 beta; also known as Rsk-2). Here we show that GSK3 isoforms are inhibited by 40% within minutes after stimulation of the rat skeletal-muscle cell line L6 with insulin-like growth factor-1 (IGF-1) or insulin. GSK3 was similarly inhibited in rabbit skeletal muscle after an intravenous injection of insulin. Inhibition resulted from increased phosphorylation of GSK3, probably at a serine/threonine residue(s), because it was reversed by incubation with protein phosphatase-2A. Rapamycin blocked the activation of p70 S6 kinase by IGF-1 in L6 cells, but had no effect on the inhibition of GSK3 or the activation of MAPKAP kinase-1 beta. In contrast, wortmannin, a potent inhibitor of PtdIns 3-kinase, prevented the inactivation of GSK3 and the activation of MAPKAP kinase-1 beta and p70 S6 kinase by IGF-1 or insulin. Wortmannin also blocked the activation of p74raf-1. MAP kinase kinase and p42 MAP kinase, but not the formation of GTP-Ras by IGF-1. The results suggest that the stimulation of glycogen synthase by insulin/IGF-1 in skeletal muscle involves the MAP-KAP kinase-1-catalysed inhibition of GSK3, as well as the previously described activation of the glycogen-associated form of protein phosphatase-1.
糖原合酶激酶-3（GSK3）在体外可被p70 S6激酶或丝裂原活化蛋白激酶激活的蛋白激酶-1β（MAPKAP激酶-1β；也称为Rsk-2）失活。在此我们表明，用胰岛素样生长因子-1（IGF-1）或胰岛素刺激大鼠骨骼肌细胞系L6后几分钟内，GSK3亚型被抑制了40%。静脉注射胰岛素后，兔骨骼肌中的GSK3也受到类似抑制。抑制是由于GSK3磷酸化增加所致，可能是在一个丝氨酸/苏氨酸残基处，因为与蛋白磷酸酶-2A孵育可使其逆转。雷帕霉素可阻断IGF-1对L6细胞中p70 S6激酶的激活，但对GSK3的抑制或MAPKAP激酶-1β的激活没有影响。相反，渥曼青霉素是一种有效的磷脂酰肌醇3激酶抑制剂，可阻止IGF-1或胰岛素对GSK3的失活以及MAPKAP激酶-1β和p70 S6激酶的激活。渥曼青霉素还可阻断p74raf-1、丝裂原活化蛋白激酶激酶和p42丝裂原活化蛋白激酶的激活，但不影响IGF-1诱导的GTP-Ras的形成。结果表明，胰岛素/IGF-1对骨骼肌中糖原合酶的刺激涉及MAP-KAP激酶-1催化的GSK3抑制，以及先前描述的糖原相关形式的蛋白磷酸酶-1的激活。
