Katagiri H, Asano T, Inukai K, Ogihara T, Ishihara H, Shibasaki Y, Murata T, Terasaki J, Kikuchi M, Yazaki Y, Oka Y
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Hongo, Japan.
Am J Physiol. 1997 Feb;272(2 Pt 1):E326-31. doi: 10.1152/ajpendo.1997.272.2.E326.
The dominant negative p85alpha regulatory subunit (delta p85alpha) of phosphatidylinositol (PI) 3-kinase or dominant negative Ras (N17Ras) was overexpressed in 3T3-L1 adipocytes using an adenovirus-mediated gene transduction system. Functional expression of delta p85alpha and N17Ras was confirmed by marked inhibition of insulin-stimulated PI 3-kinase activity and mitogen-activated protein kinase activity, respectively. N17Ras expression did not affect glucose transport activity, whereas delta p85alpha expression inhibited insulin-stimulated glucose transport with impairment of GLUT-4 translocation, although inhibition of glucose transport activity was less remarkable than that of PI 3-kinase activity in delta p85alpha-expressing cells. Thus the Ras signaling pathway does not play a major part in either translocation or intrinsic activity of glucose transporters, but PI 3-kinase activation, via phosphotyrosyl proteins and heterodimeric PI 3-kinase, plays a pivotal role in insulin-stimulated glucose transport. However, a discrepancy was observed between PI 3-kinase activity and glucose transport activity, suggesting a possibility that a different pathway(s) is involved in insulin-stimulated intrinsic activity of glucose transporters.
利用腺病毒介导的基因转导系统，在3T3-L1脂肪细胞中过表达磷脂酰肌醇（PI）3激酶的显性负性p85α调节亚基（δp85α）或显性负性Ras（N17Ras）。分别通过显著抑制胰岛素刺激的PI 3激酶活性和丝裂原活化蛋白激酶活性，证实了δp85α和N17Ras的功能性表达。N17Ras的表达不影响葡萄糖转运活性，而δp85α的表达抑制胰岛素刺激的葡萄糖转运，并损害GLUT-4转位，尽管在表达δp85α的细胞中，葡萄糖转运活性的抑制不如PI 3激酶活性的抑制显著。因此，Ras信号通路在葡萄糖转运体的转位或内在活性中均不起主要作用，但通过磷酸酪氨酸蛋白和异二聚体PI 3激酶激活PI 3激酶，在胰岛素刺激的葡萄糖转运中起关键作用。然而，在PI 3激酶活性和葡萄糖转运活性之间观察到差异，这表明可能有不同的途径参与胰岛素刺激的葡萄糖转运体的内在活性。
