Classical Genotropic Versus Kinase-Initiated Regulation of Gene Transcription by the Estrogen Receptor α

Elucidation of kinase-initiated routes by which the estrogen receptors α and β (ERα and ERβ) control gene transcription, along with evidence of distinct biologic outcomes in response to ligands that can selectively activate nongenotropic signaling of the ERs or the androgen receptor, suggest that the ERs control a range of genes wider than that regulated by their direct association with DNA. To ascertain the extent and significance of nongenotropic ER-mediated transcription, we employed transduced HeLa cells expressing wild-type ERα or the ligand binding domain of ERα localized to the cell membrane (E-Mem), the OB-6 osteoblastic cell line, MCF-7 breast carcinoma cells and uteri from mice treated with 17β-estradiol (E2), or the nongenotropic signaling activator 4-estren-3α,17β-diol (estren). E2 and estren induced ERK1/2 and Akt phosphorylation in ERα or E-Mem stably transfected HeLa cells; however, the phosphorylation kinetics differed between the two cell lines. In all four models, nongenotropic ER actions regulated a population of genes distinct from those regulated by genotropic ER actions. Specifically, the expression of Wnt2, Frizzled10, Egr-1, and c-Fos was strongly up-regulated in E-Mem-containing HeLa cells treated with E2 or estren, or in ERα-containing HeLa cells treated with estren. Up-regulation of Frizzled10 by estren was reproduced in MCF-7 cells. Egr-1 was up-regulated by both estren and E2; but complement 3, only by E2 in the uteri. Estren had no effect on complement 3, cathepsin D, progesterone receptor, bcl-2, and cyclin D1 in MCF-7 cells, whereas E2 up-regulated all these estrogen response element or activating protein-1-containing genes. These results support an extensive divergence in gene expression depending on the mode of ER activation.