In vivo and in vitro regulation of Akt activation in human endometrial cells is estrogen dependent.
Estrogen-bound estrogen receptors (ER) alpha and beta classically activate gene expression after binding to the estrogen response element in the promoter regions of target genes. Estrogen also has rapid, nongenomic effects. It activates several membranous or cytoplasmic kinase cascades, including the phosphatidylinositol 3-phosphate (PI3K/Akt) cascade, a signaling pathway that plays a key role in cell survival and apoptosis. Normal human endometrium is exposed to variable levels of steroid hormones throughout the menstrual cycle. We hypothesized that Akt phosphorylation in human endometrium may vary with the menstrual cycle and in early pregnancy and that fluctuations in estrogen level may play a role in Akt activation in endometrial cells. We analyzed Akt phosphorylation using in vivo and in vitro techniques, including Western blot, immunohistochemistry, and immunocytochemistry. Estradiol significantly increased Akt phosphorylation in endometrial cells. Rapid stimulation of Akt activation in cultured stromal cells was observed. Akt phosphorylation by estradiol was inhibited by the PI3K inhibitor, wortmannin, but not by the ER antagonist, ICI 182 780. The maximal effect on Akt activity was observed following 5-15 min of estradiol treatment. Our results suggest that estradiol may directly affect PI3K-related signaling pathway by increasing the phosphorylation of Akt in endometrial cells. Thus, estradiol may exert part of its proliferative and antiapoptotic effects by a nongenomic manner through the Akt signaling pathway.
Guzeloglu Kayisli
Ozlem
O
Division of Reproductive Endocrinology, Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, Connecticut 06520-8063, USA.
Kayisli
Umit A
UA
Luleci
Guven
G
Arici
Aydin
A
D000230:Adenocarcinoma; D015153:Blotting, Western; D001943:Breast Neoplasms; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D016889:Endometrial Neoplasms; D004717:Endometrium / Q000166:cytology / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008597:Menstrual Cycle / Q000378:metabolism; D009154:Mutation; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics; D010766:Phosphorylation; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics
D004965:Estrogen Antagonists; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D004958:Estradiol; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human