Abstract
Estrogen can modulate neuronal development and signalling by both genomic and non-genomic pathways. Many of its rapid, non-genomic effects on nervous tissue have been suggested to be mediated via the activation of the estrogen sensitive G-protein coupled receptor (GPER1 or GPR30). There has been much controversy over the cellular location, signalling properties and endogenous activators of GPER1. Here we describe the pharmacology and signalling properties of GPER1 in an immortalized embryonic hippocampal cell line, mHippoE-18. This cell line does not suffer from the inherent problems associated with the study of this receptor in native tissue or the problems associated with heterologously expression in clonal cell lines. In mHippoE-18 cells, 17β-Estradiol can mediate a dose-dependent rapid potentiation of forskolin-stimulated cyclic AMP levels but does not appear to activate the ERK1/2 pathway. The effect of 17β-Estradiol can be mimicked by the GPER1 agonist, G1, and also by tamoxifen and ICI 182,780 which activate GPER1 in a variety of other preparations. The response is not mimicked by the application of the classical estrogen receptor agonists, PPT, (an ERα agonist) or DPN, (an ERβ agonist), further suggesting that this effect of 17β-Estradiol is mediated through the activation of GPER1. However, after exposure of the cells to the GPER1 specific antagonists, G15 and G36, the stimulatory effects of the above agonists are replaced by dose-dependent inhibitions of forskolin-stimulated cyclic AMP levels. This inhibitory effect is mimicked by aldosterone in a dose-dependent way even in the absence of the GPER1 antagonists. The results are discussed in terms of possible “Biased Antagonism” whereby the antagonists change the conformation of the receptor resulting in changes in the agonist induced coupling of the receptor to different second messenger pathways.
Highlights
The G-protein coupled receptor (GPCR) sensitive to estrogen (GPER1 or GPR30) appears to mediate many of the rapid, non-genomic actions of estrogen in a wide variety of tissues, including the brain and various cancer cell lines
It can be seen that the application of both 17β-Estradiol and the GPER1 agonist, G1, produced dose-dependent increases in forskolin-stimulated cyclic AMP levels in mHippoE-18 cells (Fig 1)
The present study has investigated the signalling properties of the estrogen activated G-protein coupled receptor (GPER1) in the immortalized hippocampal cell line, mHippoE-18
Summary
The G-protein coupled receptor (GPCR) sensitive to estrogen (GPER1 or GPR30) appears to mediate many of the rapid, non-genomic actions of estrogen in a wide variety of tissues, including the brain and various cancer cell lines (see [1]). Rapid non-genomic responses to estrogens have been reported to be due to the activation of a range of additional plasma membrane located receptors in a wide variety of cell types in the nervous system (see [11, 12]). The classical estrogen receptors, ERα and ERβ, have been suggested to have a plasma membrane location in nervous tissue, where they can mediate some of the rapid non-genomic actions of estrogen (see [12]). The molecular identity of the latter two receptors remains unknown
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