Changes in Sodium Pump Expression Dictate the Effects of Ouabain on Cell Growth
Changes in Sodium Pump Expression Dictate the Effects of Ouabain on Cell Growth
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DOI：
10.1074/jbc.m808355200
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发表时间：
2009-05-29
影响因子：
4.8
通讯作者：
Xie, Zijian
中科院分区：
文献类型：
--
作者：
Tian, Jiang;Li, Xin;Xie, Zijian
在这里，我们发现哇巴因诱导的细胞生长调节本质上与细胞内 Na/K-ATP 酶含量的变化通过磷酸肌醇 3-激酶 (PI3K)/Akt/哺乳动物雷帕霉素靶标 (mTOR) 途径相关。哇巴因可增加 LLC-PK1、人乳腺癌 (BT20) 和前列腺 (DU145) 癌细胞中 Na/K-ATP 酶的内吞作用和降解。然而，哇巴因刺激 PI3K/Akt/mTOR 通路，从而上调 LLC-PK1 中 Na/K-ATPase 的表达，但不上调 BT20 和 DU145 细胞中的 Na/K-ATPase 表达。这种上调足以补充 Na/K-ATP 酶的质膜池并刺激 LLC-PK1 细胞的细胞增殖。另一方面，哇巴因会导致 Na/K-ATP 酶逐渐耗尽，并增加细胞周期抑制剂 p21(cip) 的表达，从而抑制 BT20 和 DU145 细胞的细胞增殖。我们一致地观察到，小干扰 RNA 介导的 Na/K-ATPase 敲低足以诱导 p21cip 的表达并减缓 LLC-PK1 细胞的增殖。此外，这种敲低将哇巴因的生长刺激作用转化为 LLC-PK1 细胞的生长抑制作用。从机制上讲，Src 和 Caveolin-1 都是哇巴因诱导的 Akt 激活和 Na/K-ATPase 上调所必需的。此外，在 LLC-PK1 细胞中，雷帕霉素对 PI3K/Akt/mTOR 通路的抑制完全阻断哇巴因诱导的 Na/K-ATPase 表达，并将哇巴因诱导的生长刺激转化为生长抑制。综上所述，我们得出结论，Na/K-ATP酶表达的变化决定了哇巴因对细胞的生长调节作用。
Here we show that ouabain-induced cell growth regulation is intrinsically coupled to changes in the cellular amount of Na/K-ATPase via the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. Ouabain increases the endocytosis and degradation of Na/K-ATPase in LLC-PK1, human breast (BT20), and prostate (DU145) cancer cells. However, ouabain stimulates the PI3K/Akt/mTOR pathway and consequently up-regulates the expression of Na/K-ATPase in LLC-PK1 but not BT20 and DU145 cells. This up-regulation is sufficient to replete the plasma membrane pool of Na/K-ATPase and to stimulate cell proliferation in LLC-PK1 cells. On the other hand, ouabain causes a gradual depletion of Na/K-ATPase and an increased expression of cell cycle inhibitor p21(cip), which consequently inhibits cell proliferation in BT20 and DU145 cells. Consistently, we observe that small interfering RNA-mediated knockdown of Na/K-ATPase is sufficient to induce the expression of p21cip and slow the proliferation of LLC-PK1 cells. Moreover, this knockdown converts the growth stimulatory effect of ouabain to growth inhibition in LLC-PK1 cells. Mechanistically, both Src and caveolin-1 are required for ouabain-induced activation of Akt and up-regulation of Na/K-ATPase. Furthermore, inhibition of the PI3K/Akt/mTOR pathway by rapamycin completely blocks ouabain-induced expression of Na/K-ATPase and converts ouabain-induced growth stimulation to growth inhibition in LLC-PK1 cells. Taken together, we conclude that changes in the expression of Na/K-ATPase dictate the growth regulatory effects of ouabain on cells.