Yang Wei-Rong, Wang Yong, Wang Yi, Zhang Jiao-Jiao, Zhang Jia-Hua, Lu Cheng, Wang Xian-Zhong
College of Animal Science and Technology, Southwest University, Chongqing, P. R. China; Chongqing Key Laboratory of Forage and Herbivore, Southwest University, Chongqing, P. R. China.
Mol Reprod Dev. 2015 Apr;82(4):305-14. doi: 10.1002/mrd.22473. Epub 2015 Mar 4.
Mammalian target of rapamycin (mTOR) is known to be involved in mammalian cell proliferation, while S-phase kinase-associated protein 2 (SKP2) plays a vital role in the cell cycle. Within the testis, estrogen also plays an important role in Sertoli cell proliferation, although it is not clear how. The present study asked if mTOR is involved in 17β-estradiol-dependent Sertoli cell proliferation. We specifically assessed if extracellular signal-regulated kinase 1/2 (ERK1/2) and/or phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) exert convergent effects toward the activation of mTOR signaling, and if this signaling regulates the expression of SKP2 through retinoblastoma (RB) and early mitotic inhibitor 1 (EMI1) protein and on CCNE1 and CCND1 mRNA levels. Treatment with 17β-estradiol for 15-90 min activated mTOR, with mTOR phosphorylation peaking after 30 min. U0126 (5 μM), a specific inhibitor of (MEK1/2), and 10-DEBC (2 μM), a selective inhibitor of AKT, both significantly reduced 17β-estradiol-induced phosphorylation of mTOR. Rapamycin suppressed 17β-estradiol-induced Sertoli cell proliferation, appearing to act by reducing the abundance of SKP2, CCND1, and CCNE1 mRNA as well as RB and EMI1 protein. These data indicated that 17β-estradiol enhances Sertoli cell proliferation via mTOR activation, which involves both ERK1/2 and PI3K/AKT signaling. Activated mTOR subsequently increases SKP2 mRNA and protein expression by enhancing the expression of CCND1 and CCNE1, and inhibits SKP2 protein degradation by increasing EMI1 abundance.
已知雷帕霉素的哺乳动物靶点（mTOR）参与哺乳动物细胞增殖，而S期激酶相关蛋白2（SKP2）在细胞周期中起关键作用。在睾丸内，雌激素在支持细胞增殖中也发挥重要作用，尽管其作用机制尚不清楚。本研究探讨mTOR是否参与17β-雌二醇依赖性支持细胞增殖。我们具体评估细胞外信号调节激酶1/2（ERK1/2）和/或磷酸肌醇3激酶/蛋白激酶B（PI3K/AKT）对mTOR信号激活是否具有趋同作用，以及该信号是否通过视网膜母细胞瘤（RB）和早期有丝分裂抑制剂1（EMI1）蛋白调节SKP2的表达以及CCNE1和CCND1 mRNA水平。用17β-雌二醇处理15 - 90分钟可激活mTOR，mTOR磷酸化在30分钟后达到峰值。U0126（5μM），一种（MEK1/2）的特异性抑制剂，以及10 - DEBC（2μM），一种AKT的选择性抑制剂，均显著降低17β-雌二醇诱导的mTOR磷酸化。雷帕霉素抑制17β-雌二醇诱导的支持细胞增殖，似乎是通过降低SKP2、CCND1和CCNE1 mRNA以及RB和EMI1蛋白的丰度来发挥作用。这些数据表明，17β-雌二醇通过mTOR激活增强支持细胞增殖，这涉及ERK1/2和PI3K/AKT信号。激活的mTOR随后通过增强CCND1和CCNE1的表达增加SKP2 mRNA和蛋白表达，并通过增加EMI1丰度抑制SKP2蛋白降解。
