Requirement of Ras-dependent pathways for activation of the transforming growth factor beta3 promoter by estradiol.
It has been previously observed that the transforming growth factor beta3 (TGFbeta3) gene can be activated by both estradiol (E(2)) and selective estrogen receptor modulators (SERMs) in vivo but that only SERMs have a potent stimulatory effect on the TGFbeta3 promoter in cultured cells. We demonstrate in this report that E(2) can act also as a potent inducer of the TGFbeta3 promoter via a novel and specific estrogen receptor (ER)alpha-mediated mechanism. Our results show that treatment with epidermal growth factor or transfection of a constitutively active Ras mutant allows E(2) to induce the TGFbeta3 promoter via ERalpha in cotransfected HeLa and osteosarcoma MG63 cells. Both protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) inhibitors can block the combined stimulatory effect of E(2) and epidermal growth factor/Ras. However, E(2) induction of the TGFbeta3 promoter was found to be unaffected by mutation of ERalpha serine 118, a well-characterized target of MAPK. Progressive deletion analysis of the ERalpha amino-terminal region delineated three separate domains modulating the E(2)/activated Ras response, revealing a complex functional organization of the ERalpha A/B domain required for regulation of the TGFbeta3 promoter. In addition, PKC and MAPK inhibitors had no effect on the induction of TGFbeta3 promoter activity by the SERM EM-652. These results indicate that induction of the TGFbeta3 promoter by the E(2)/ERalpha complex requires the concomitant activation of PKC and MAPK signaling and provide a novel framework for the design of more effective estrogen-based therapeutic strategies.
Lu
D
D
Molecular Oncology Group, McGill University Health Center, Montréal, Québec, Canada H3A 1A1.
Giguère
V
V
D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha; D017353:Gene Deletion; D006367:HeLa Cells; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009154:Mutation / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000187:drug effects* / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011960:Receptors, Estrogen / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000235:genetics*; D053782:Transforming Growth Factor beta3; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000502:physiology*
D004791:Enzyme Inhibitors; D047628:Estrogen Receptor alpha; D011960:Receptors, Estrogen; D016212:Transforming Growth Factor beta; D053782:Transforming Growth Factor beta3; D004958:Estradiol; D004815:Epidermal Growth Factor; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins