Huang C, Ma W Y, Dong Z
The Hormel Institute, University of Minnesota, Austin 55912, USA.
Mol Cell Biol. 1996 Nov;16(11):6427-35. doi: 10.1128/MCB.16.11.6427.
Phosphatidylinositol 3-kinase (PI 3-kinase) plays a role in a variety of biological processes, including regulation of gene expression, cell growth, and differentiation. However, little is known about its role in the cytoplasmic events involved in epidermal growth factor (EGF)-induced transduction of signals to the transcriptional machinery of the nucleus and in EGF-induced cell transformation. In this study, we examined whether PI 3-kinase is a mediator for the activation of AP-1 and neoplastic transformation by EGF in the murine epidermal cell line JB6. The results showed the following. (i) EGF not only induced a high level of PI 3-kinase activity by itself but also enhanced insulin-induced PI 3-kinase activity in JB6 P+ cells, the EGF-induced PI-3 kinase activity could be blocked by constitutive overexpression of a dominant negative P85 subunit of PI 3-kinase (deltaP85), and insulin could markedly promote EGF-induced AP-1 activity in a dose-dependent manner in JB6 P+ cells as well as promote EGF-induced JB6 P+ cell transformation. (ii) Inhibition of PI-3 kinase with wortmannin or LY294002 markedly decreased the AP-1 activity induced by insulin, EGF, or EGF and insulin in a dose-dependent manner, while wortmannin did not block UVB-induced AP-1 activity. (iii) AP-1 activation by insulin, EGF, or EGF and insulin could be completely inhibited by overexpression of deltaP85 in all the dose and time courses studied. (iv) Inhibitors of PI 3-kinase (wortmannin and LY294002) and stable overexpression of deltaP85 inhibited EGF-induced transformation but had no significant inhibitory effect on cell proliferation induced by EGF or EGF and insulin. These results demonstrate for the first time that PI 3-kinase appears to be required for EGF- or insulin-induced AP-1 transactivation and cell transformation but not cell proliferation in JB6 cells.
磷脂酰肌醇3激酶（PI 3激酶）在多种生物学过程中发挥作用，包括基因表达调控、细胞生长和分化。然而，对于其在表皮生长因子（EGF）诱导的信号转导至细胞核转录机制以及EGF诱导的细胞转化所涉及的细胞质事件中的作用，人们了解甚少。在本研究中，我们检测了PI 3激酶是否是EGF在小鼠表皮细胞系JB6中激活AP - 1和肿瘤转化的介质。结果如下：（i）EGF自身不仅诱导高水平的PI 3激酶活性，还增强了胰岛素诱导的JB6 P +细胞中的PI 3激酶活性，EGF诱导的PI - 3激酶活性可被PI 3激酶显性负性P85亚基（deltaP85）的组成型过表达所阻断，并且胰岛素能以剂量依赖方式显著促进EGF诱导的JB6 P +细胞中的AP - 1活性以及促进EGF诱导的JB6 P +细胞转化。（ii）渥曼青霉素或LY294002抑制PI - 3激酶以剂量依赖方式显著降低了胰岛素、EGF或EGF与胰岛素诱导的AP - 1活性，而渥曼青霉素不阻断UVB诱导的AP - 1活性。（iii）在所有研究的剂量和时间进程中，deltaP85的过表达可完全抑制胰岛素、EGF或EGF与胰岛素诱导的AP - 1激活。（iv）PI 3激酶抑制剂（渥曼青霉素和LY294002）以及deltaP85的稳定过表达抑制了EGF诱导的转化，但对EGF或EGF与胰岛素诱导的细胞增殖没有显著抑制作用。这些结果首次证明PI 3激酶似乎是EGF或胰岛素诱导的AP - 1反式激活和细胞转化所必需的，但在JB6细胞中不是细胞增殖所必需的。
