磷脂酰肌醇-3-激酶在胰岛素与表皮生长因子激活MAPK信号通路中的不同作用

目的　研究磷脂酰肌醇 3 激酶 (phosphatidylinositol3 kinase, PI3K)在胰岛素和表皮生长因子 (epidermalgrowthfactor, EGF)刺激丝裂原激活的蛋白激酶 (mitogen activatedproteinkinase,MAPK)信号通路中的作用。方法　主要应用免疫印迹方法分析MAPK的磷酸化水平,利用PI3K特异性抑制剂wortmannin了解PI3K在其中所起的作用。结果　胰岛素和EGF均能有效、快速地刺激MAPK的磷酸化;wort mannin抑制胰岛素刺激的MAPK磷酸化,但对EGF刺激的MAPK磷酸化却没有明显影响。与此相反,胰岛素和EGF刺激的蛋白激酶B的磷酸化,均可被wortmannin同样有效地抑制。另外,wortmannin抑制胰岛素刺激的MAPK磷酸化具浓度依赖性;其不能抑制EGF刺激的MAPK磷酸化的性质并不随EGF刺激浓度的改变而改变。结论　PI3K在胰岛素和EGF刺激的MAPK磷酸化信号通路中起不同的作用。

Differential roles of phosphatidylinositol 3-kinase in mitogen-activated prote in kinase activation by insulin and epidermal growth factor

Aim To investigate the roles of phosphatidylinositol 3 -kinase (PI3K) in the mitogen-activated protein kinase (MAPK) activation by in sulin and epidermal growth factor (EGF). Methods Phosphorylated MAPK, Akt (also termed protein kinase B) and total protein level of MAPK were d etermined by Western blotting using phospho- or non-phospho-state specific an tibodies;the roles of PI3K in these signaling transduction pathways were assess ed by use of PI3K specific inhibitor wortmannin.Results Both in sulin and EGF rapidly stimulated MAPK phosphorylation; wortmannin totally blocke d the MAPK phosphorylation stimulated by insulin, but not by EGF.By contrast, wo rtmannin equally inhibited Akt phosphorylation stimulated by both insulin and EG F. Moreover, wortmannin inhibited insulin-stimulated MAPK phosphorylation in a concentration-dependent manner,and the inability of wortmannin to inhibit EGF -stimulated MAPK phosphorylation was not changed with the use of low concentrat ions of EGF.Conclusion PI3K plays different roles in the MAPK a ctivation induced by insulin and EGF.