Effect of estrogen and inhibition of phosphatidylinositol-3 kinase on Akt and FOXO1 in rat uterus

Institute of Physiology, Pécs University Medical School, Szigeti út 12, Pécs H7624, Hungary.
Steroids (Impact Factor: 2.64). 06/2007; 72(5):422-8. DOI: 10.1016/j.steroids.2007.03.001
Source: PubMed


The importance of FOXO transcription factors in regulating different aspects of cellular homeostasis and apoptosis has become apparent. Akt/protein kinase B has been shown to phosphorylate and inactivate members of FOXO family of transcription factors. Akt and its upstream regulator, phosphatidylinositol-3 kinase (PI3K) are involved in rapid action of estrogen (E2) in different cells and tissues. The aim of the present study was to analyze the E2/PI3K/Akt/FOXO pathway in rat uterus. In response to E2, phosphorylation of Akt/PKB on Ser473 and FOXO1 on Ser256 and Thr24 residues increased but with distinct kinetics, regulating the activation and inactivation of Akt and FOXO1 proteins, respectively. The antiestrogen ICI 182,780 prevented E2 induced Akt activation suggesting that estrogen receptors mediate this effect of E2. Intrauterine injection of Wortmannin caused a decrease in the phosphorylation of Ser473 of Akt, and attenuated phosphorylation of its downstream target FOXO1 at Ser256 and at Thr24. However, the effect of E2 on phosphorylation of Thr24 showed a kinetic pattern distinct from that of Ser256. Our results suggest that the E2/PI3K/Akt/FOXO1 pathway in rat uterus is functioning even at the lack of ovarian hormones and responses to E2 treatment. Estradiol increases Akt phosphorylation through a Wortmannin sensitive way, presumably involving PI3K. The present work shows that PI3K plays a crucial role in the phosphorylation and inactivation of FOXO1 in vivo, indicating that the regulation of this transcription factor is a more complex event in uterine cells requiring further investigations.

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    • "All of genes possess more than 5 edges, and many possible target genes were predicted in the estrogen-mediated signal pathways. For example, insulin-like growth factor 1 (IGF1R) shares important signaling cascades with estrogen receptor [29], while forkhead box O1 (FOXO1) is involved in the estrogen mediated E2/PI3K/Akt/FOXO1 pathway [30]. It has been reported that cervical SCC is a hormone-associated gynecological disease [31]. "
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    • "Estrogen exerts protective effects against oxidative stress in many tissues including the heart, brain, kidney and bone mainly through an anti-apoptotic mechanism [62], [63], [64], [65], [66], [67]. Only recently has estrogen's anti-apoptotic effect been linked to the inhibition of the PI3K pathway via control of Foxo 1 transcription [68]. The PR is reported to regulate the transcriptional activities of Foxos, especially Foxo1, which controls endometrial decidualization [69], [70]. "
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