Nagasaka Y, Kaku K, Nakamura K, Kaneko T
Department of Biochemistry, Yamaguchi University School of Medicine, Japan.
Biochem Biophys Res Commun. 1994 Jul 29;202(2):1104-12. doi: 10.1006/bbrc.1994.2042.
Effects of cAMP on insulin-stimulated mitogen-activated protein (MAP) kinase pathway were examined using rat hepatoma H4EII cells. MAP kinase was rapidly activated and reached a peak 3 min after the stimulation by insulin. Forskolin (1 microM) and 8(4-chlorophenylthio)cAMP (8-CPT-cAMP) (0.1 mM) inhibited the insulin-stimulated MAP kinase activity. Pretreatment of the cells with H-8 (50 microM), a cAMP-dependent protein kinase inhibitor, enhanced the insulin-stimulated MAP kinase activity and partially restored the inhibitory effect of cAMP. Furthermore, insulin-induced phosphorylation of MAP kinase was inhibited by 8-CPT-cAMP, and the inhibition was restored by H-8. 8-CPT-cAMP did not inhibit the autophosphorylation of insulin receptor. These data indicate that elevation of intracellular cAMP blocks the insulin-stimulated MAP kinase pathway downstream of insulin receptor.
利用大鼠肝癌H4EII细胞研究了环磷酸腺苷（cAMP）对胰岛素刺激的丝裂原活化蛋白（MAP）激酶途径的影响。胰岛素刺激后，MAP激酶迅速被激活，并在3分钟后达到峰值。福斯高林（1微摩尔）和8-（4-氯苯硫基）环磷酸腺苷（8-CPT-cAMP）（0.1毫摩尔）抑制胰岛素刺激的MAP激酶活性。用cAMP依赖性蛋白激酶抑制剂H-8（50微摩尔）预处理细胞，可增强胰岛素刺激的MAP激酶活性，并部分恢复cAMP的抑制作用。此外，8-CPT-cAMP抑制胰岛素诱导的MAP激酶磷酸化，而H-8可恢复这种抑制作用。8-CPT-cAMP不抑制胰岛素受体的自身磷酸化。这些数据表明，细胞内cAMP水平升高会在胰岛素受体下游阻断胰岛素刺激的MAP激酶途径。
