Lianguzova M S, Chuĭkin I A, Nordheim A, Pospelov V A
Tsitologiia. 2006;48(7):560-8.
Murine embryonic stem (mES) cells can proliferate independently of the presence of growth factors in the medium. It is yet unknown what intrinsic activity triggers cell cycle events in mES cells. Here we investigated the contribution of the PI3-kinase cascade to autonomous proliferation of mES cell using PI3-kinase inhibitors wortmannin and LY294002. Wortmannin displays a weaker inhibitory effect on phosphorylation of PI3-kinase pathway target PKB as compared with LY294002, and does not downregulate mES cells proliferation, while LY294002 causes a strong decrease in the share of cells in S-phase and accumulation of cells in G1 phase. Both inhibitors cause significant decrease in cyclin D1 amount. The treatment with LY294002, rather than with wortmannin results in a decrease of cyclin E amount and cyclin E-assossiated kinase activity. In mES cells, inactivation of PI3-kinase-dependent pathway and G1 arrest are not accompanied by induction of p27kip 1 transcription and accumulation of this inhibitor of cyclin-cdk complexes at the protein level, implying that these events accomplished by some p27kip 1-independent mechanism. Both LY294002 and wortmannin cause apoptotic death of mES cells and downregulate the growth of population. Thus, inactivation of PI3-kinase in mES cells may lead to apoptosis rather than to cell cycle arrest.
小鼠胚胎干细胞（mES细胞）能够在培养基中不存在生长因子的情况下独立增殖。目前尚不清楚是什么内在活性触发了mES细胞中的细胞周期事件。在这里，我们使用PI3激酶抑制剂渥曼青霉素和LY294002研究了PI3激酶级联对mES细胞自主增殖的作用。与LY294002相比，渥曼青霉素对PI3激酶途径靶点PKB磷酸化的抑制作用较弱，并且不会下调mES细胞的增殖，而LY294002会导致S期细胞比例大幅下降以及G1期细胞积累。两种抑制剂都会导致细胞周期蛋白D1含量显著降低。用LY294002而非渥曼青霉素处理会导致细胞周期蛋白E含量和细胞周期蛋白E相关激酶活性降低。在mES细胞中，PI3激酶依赖性途径的失活和G1期阻滞并不伴随着p27kip 1转录的诱导以及该细胞周期蛋白-cdk复合物抑制剂在蛋白质水平的积累，这意味着这些事件是通过某种不依赖p27kip 1的机制完成的。LY294002和渥曼青霉素都会导致mES细胞凋亡死亡并下调细胞群体的生长。因此，mES细胞中PI3激酶的失活可能导致细胞凋亡而非细胞周期停滞。
