Interplay of estrogen receptors and GPR30 for the regulation of early membrane initiated transcriptional effects: A pharmacological approach

Estrogens exert their effect through ERα and ERβ intracellular transcription factors and rapid, usually membrane-initiated receptors, influencing cytosolic signaling and transcription. The nature of extranuclear estrogen elements has not been elucidated so far; classical or alternatively transcribed ER isoforms (ERα36, ERα46) anchored to the plasma membrane and GPR30 (GPER1) have been reported to exert early estrogen actions. Here, we used E2–BSA, an impermeable estradiol analog for a transcriptome analysis in four GREP1 positive breast cancer cell lines with different estrogen receptor profiles (T47D, MCF-7, MDA-MB-231 and SKBR3) in order to evaluate GPER1 transcriptional effects. Early effects of E2–BSA were assayed after 3 h of incubation, in the absence/presence of ICI182,780 (ER-inhibitor) or G15 (GREP1-specific inhibitor). E2–BSA specifically modified 277–549 transcripts in the different cell lines. Two different clusters of transcripts could be identified: (1) the majority of transcripts were inhibited by both ICI182,780 and G15, suggesting an interaction of E2–BSA with a common ER-related element, or a direct ER–GPER1 interaction; (2) a small number of G15-only modified transcripts, in two cell lines (T47D and SKBR3 cells), indicative of specific GPER1-related effects. The latter transcripts were significantly related to pathways including FOXA2/FOXA3 transcription factor networks, RNA-Polymerases Transcription Regulation and lipid metabolism, while ICI/G15 inhibited transcripts affected pathways related to apoptosis, erythropoietin signaling, metabolic effects through the citric acid cycle, IL-4 and IL-5 mediated events and homologous DNA recombination. Finally, we review the current literature of GPER1 actions, in view of our results of ER-dependent and independent GPER1-modified pathways.

► We estimated GPR30 membrane initiated estrogen effects in breast cancer cell lines.
► G15 inhibited most E2–BSA modified transcripts.
► Most of these transcripts were also inhibited by ICI182,780.
► A number of G15 only inhibited transcripts indicate specific GPR30-related effects.
► We also review the current literature of GPR30 actions.