Progesterone Receptor Regulation in Uterine Cells:Stimulation by Estrogen, Cyclic Adenosine 3′,5′-Monophosphate, and Insulin-Like Growth Factor I andSuppression by Antiestrogens and Protein KinaseInhibitors*

Abstract

Primary uterine cell cultures were used to study multifactor regulation of progesterone receptor (PR) and the signal transduction pathways which may serve to mediate that regulation. Increases in intracellular cAMP, brought about by treatment with cholera toxin plus isobutyl methyl xanthine or by addition of 8-bromo-cAMP, result in 6- to 7-fold increases in the intracellular content of PR as monitored by [3H]R5020 binding and by Western immunoblot using anti-PR antibodies. In these primary cultures of uterine cells isolated from 19-day-old immature rats, 8-bromo-cAMP evokes significant increases in PR by 8 h with maximal increases by 24 h. This time course and magnitude of PR stimulation are similar to those evoked by maximally effective concentrations of estradiol (3 x 10(-9) M) or IGF-I (20 ng/ml). Dose-response studies reveal that 10(-6) to 10(-4) M concentrations of 8-bromo-cAMP (8-Br-cAMP) elicit a maximal response. In contrast, 8-bromo-cGMP over a wide concentration range was unable to elevate cellular PR levels. Under these culture conditions, cell proliferation was not altered by treatment with any of these agents. Although estrogen, cAMP, and insulin-like growth factor I (IGF-I) may act via different pathways to increase PR, the effects evoked by maximally effective concentrations of these agents are not additive implying involvement of a common component. The increases in PR evoked by estradiol, cAMP, or IGF-I are markedly suppressed by treatment with antiestrogen (ICI 164,384) or the cyclic nucleotide-dependent protein kinase inhibitor H8 or the protein kinase A inhibitor PKI, indicating the involvement of the estrogen receptor and phosphorylation pathways in PR regulation by these three agents. The present studies identify cAMP, as well as estrogen and IGF-I, as important regulators of the level of PR in uterine cells and suggest that multiple factors, including those affecting intracellular cAMP levels, might influence responsiveness to progestins via regulation of the intracellular PR content.

Differential Spatiotemporal Regulation of Lactoferrin and Progesterone Receptor Genes in the Mouse Uterus by Primary Estrogen, Catechol Estrogen, and Xenoestrogen1

“…However, there is evidence that these genes can be up-regulated by many other factors. For example, although the LF gene is inducible in the uterus and mammary gland by epidermal growth factor (32) and PRL (15,33), respectively, the PR gene is known to be induced by dopamine, cAMP, and growth factors (17,34,35). In the present investigation, the increased accumulation of their mRNAs in the mouse uterus after exposure to E 2 or 4-OH-E 2 was anticipated.…”

Involvement of cyclic AMP response element binding protein (CREB) and estrogen receptor phosphorylation in the synergistic activation of the estrogen receptor by estradiol and protein kinase activators

“…In estrogen receptor (ER)-containing breast cancer cells, we and others have shown that PKA activators enhance the transcription of estrogen regulated genes such as pS2, cathepsin D or progesterone receptor [2][3][4] and that this effect is blocked by the pure antiestrogen ICI 164,384 [2,4]. These results are also observed in transient transfection experiments, with the magnitude of transcriptional enhancement dependent on the cellular context and gene construct used [5][6][7][8][9].…”

Epidermal Growth Factor and Transforming Growth Factor-α Stimulate the Proliferation of Mouse Uterine Stromal Cells

“…Progesterone is essential for the growth of uterine stromal cells. The increase in the progesterone receptor level is evoked by estrogen (Aronica and Katzenellenbogen, 1991). The mechanism of cooperative action between E 2 and P needs to be clarified.…”