Constitutive activation of protein kinase Bα by membrane targeting promotes glucose and system A amino acid transport, protein synthesis, and inactivation of glycogen synthase kinase 3 in L6 muscle cells
Constitutive activation of protein kinase Bα by membrane targeting promotes glucose and system A amino acid transport, protein synthesis, and inactivation of glycogen synthase kinase 3 in L6 muscle cells
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DOI：
10.2337/diabetes.47.7.1006
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发表时间：
1998-07-01
期刊：
影响因子：
7.7
通讯作者：
Hundal, HS
中科院分区：
文献类型：
--
作者：
Hajduch, E;Alessi, DR;Hundal, HS
磷脂酰肌醇3-激酶（PI 3-kinase）参与了许多细胞过程的调节，包括胰岛素诱导的糖原合成酶激酶3（GSK-3）和葡萄糖转运的调节。胰岛素诱导的GSK-3失活是由PI 3-激酶的下游靶蛋白激酶B（PKB）介导的，PKB在其他胰岛素刺激反应中的作用目前尚不清楚。在这项研究中，我调查是否葡萄糖的摄取，系统A的氨基酸运输，和细胞蛋白质合成的调节PKB α在L 6骨骼肌细胞。稳定过表达野生型PKB α（wtPKB α）或组成型活性膜靶向PKBa（mPKB α）的L 6细胞分别显示PRE活性增加3倍和15倍。wtPKB α和mPKB α表达均导致葡萄糖和甲基氨基异丁酸（系统A氨基酸转运蛋白的底物）的基础摄取显著增加，至少达到用胰岛素处理的对照细胞中观察到的水平。促进葡萄糖转运的刺激，部分是通过增加GLUT 4转运到质膜，也通过增加GLUT 3的细胞合成。在没有胰岛素的情况下，只有表达组成型活性PKB α的肌细胞显示蛋白质合成的显著增加和GSK-3的抑制。我们的研究结果表明，骨骼肌中PKBa的组成性激活刺激葡萄糖，系统A氨基酸和蛋白质合成的摄取，并促进GSK-3的失活。这些观察结果意味着PKB α可能在骨骼肌中这些过程的胰岛素调节控制中发挥作用。
Phosphatidylinositol 3-kinase (PI 3-kinase) has been implicated in the regulation of numerous cellular processes, including the insulin-induced regulation of glycogen synthase kinase 3 (GSK-3) and glucose transport. The hormonal-induced inactivation of GSK-3 is mediated by protein kinase B (PKB), a downstream target of PI 3-kinase, whose involvement in other insulin-stimulated responses remains poorly defined at present. In this study, me investigated whether the uptake of glucose, system A amino acid transport, and cellular protein synthesis are regulated by PKB alpha in L6 skeletal muscle cells. L6 cells stably overexpressing wild-type PKB alpha (wtPKB alpha) or a constitutively active membrane-targeted PKBa (mPKB alpha) showed a 3- and 15-fold increase in PRE activity, respectively. Both wtPKB alpha and mPKB alpha expression led to a significant increase in the basal uptake of glucose and methyl-aminoisobutyric acid (a substrate for the system A amino acid transporter), at least to a level seen in control cells treated with insulin. The stimulation in glucose transport was facilitated, in part, by the increased translocation of GLUT4 to the plasma membrane and also through an increase in the cellular synthesis of GLUT3. In the absence of insulin, only muscle cells expressing the constitutively active PKB alpha showed a significant increase in protein synthesis and an inhibition in GSK-3. Our results indicate that constitutive activation of PKBa in skeletal muscle stimulates the uptake of glucose, system A amino acids, and protein synthesis and promotes the inactivation of GSK-3. These observations imply that PKB alpha may have a role in the insulin-regulated control of these processes in skeletal muscle.