Research Institute of Pharmaceutical Sciences, NeuroVascular Coordination Research Center, College of Pharmacy, Seoul National University, Seoul 151-742, Korea.
Exp Mol Med. 2010 Apr 30;42(4):294-301. doi: 10.3858/emm.2010.42.4.028.
Under hypoxia, mouse embryonic stem cells (mESCs) lose their self-renewal activity and display an early differentiated morphology mediated by the hypoxia-inducible factor-1 alpha (HIF-1 alpha). Previous studies have demonstrated that PKC-delta is activated by hypoxia and increases the protein stability and transcriptional activity of HIF-1 alpha in human cancer cells. Furthermore, activation of PKC-delta mediates cardiac differentiation of ESCs and hematopoietic stem cells. However, the role of PKC-delta in hypoxia-induced early differentiation of mESCs remains largely unknown. Here, we show the inhibition of PKC-delta activity prevents the early differentiation of mESCs under hypoxia using PKC-delta inhibitors, GF 109203X and rottlerin. Reduction of PKC-delta activity under hypoxia effectively decreased HIF-1 alpha protein levels and substantially recovered the expression of LIF-specific receptor (LIFR) and phosphorylated-STAT3 in mESCs. Furthermore, PKC-delta inhibitors aid to sustain the expression of self-renewal markers and suppress the expression of early differentiation markers in mESCs under hypoxia. Taken together, these results suggest that PKC-delta inhibitors block the early differentiation of mESCs via destabilization of HIF-1 alpha under hypoxia.
在缺氧条件下，小鼠胚胎干细胞（mESCs）失去自我更新能力，并表现出由缺氧诱导因子-1α（HIF-1α）介导的早期分化形态。先前的研究表明，蛋白激酶 C-δ（PKC-delta）被缺氧激活，并增加人类癌细胞中 HIF-1α的蛋白稳定性和转录活性。此外，PKC-delta 的激活介导了 ESCs 和造血干细胞的心脏分化。然而，PKC-delta 在 mESCs 缺氧诱导的早期分化中的作用在很大程度上仍不清楚。在这里，我们使用 PKC-delta 抑制剂 GF 109203X 和罗特林（rottlerin）表明，PKC-delta 活性的抑制可防止 mESCs 在缺氧条件下的早期分化。缺氧下 PKC-delta 活性的降低可有效降低 HIF-1α蛋白水平，并显著恢复 mESCs 中 LIF 特异性受体（LIFR）和磷酸化-STAT3 的表达。此外，PKC-delta 抑制剂有助于维持 mESCs 在缺氧条件下的自我更新标志物的表达，并抑制早期分化标志物的表达。综上所述，这些结果表明，PKC-delta 抑制剂通过在缺氧条件下破坏 HIF-1α的稳定性来阻止 mESCs 的早期分化。
