Kovacina K S, Yonezawa K, Brautigan D L, Tonks N K, Rapp U R, Roth R A
Department of Pharmacology, Stanford University School of Medicine, California 94305-5332.
J Biol Chem. 1990 Jul 25;265(21):12115-8.
Insulin was found to stimulate the serine/threonine kinase activity of the proto-oncogene product Raf-1. This stimulation was observed in HeLa, NIH 3T3, and Chinese hamster ovary cells, all overexpressing the human insulin receptor. In the HeLa cells, 100 pM insulin gave a significant increase in Raf-1 kinase activity, and 100 nM insulin caused a maximal 2-5-fold increase in activity. The increase in activity was detected after 2 min of insulin treatment and peaked after 5 min. In addition to stimulating Raf-1 kinase activity, insulin caused a shift in the electrophoretic mobility of the Raf-1 protein and an increase in the amount of serine phosphorylation of Raf-1. Moreover, a serine/threonine-specific phosphatase, phosphatase 1, but not two tyrosine-specific phosphatases, was found to deactivate the insulin-activated Raf-1 kinase activity. These findings indicate that insulin activates the serine/threonine kinase activity of the Raf-1 proto-oncogene by increasing its content of phosphoserine.
胰岛素被发现可刺激原癌基因产物Raf-1的丝氨酸/苏氨酸激酶活性。在过表达人胰岛素受体的HeLa细胞、NIH 3T3细胞和中国仓鼠卵巢细胞中均观察到这种刺激作用。在HeLa细胞中，100 pM胰岛素可使Raf-1激酶活性显著增加，100 nM胰岛素可使活性最大增加2至5倍。胰岛素处理2分钟后检测到活性增加，并在5分钟后达到峰值。除了刺激Raf-1激酶活性外，胰岛素还导致Raf-1蛋白的电泳迁移率发生变化，并使Raf-1的丝氨酸磷酸化量增加。此外，发现一种丝氨酸/苏氨酸特异性磷酸酶，即磷酸酶1，而非两种酪氨酸特异性磷酸酶，可使胰岛素激活的Raf-1激酶活性失活。这些发现表明，胰岛素通过增加Raf-1原癌基因的磷酸丝氨酸含量来激活其丝氨酸/苏氨酸激酶活性。
