Estrogen- and xenoestrogen-induced ERK signaling in pituitary tumor cells involves estrogen receptor-α interactions with G protein-αi and caveolin I

Abstract

Multiple physiologic estrogens (estradiol, estriol, and estrone), as well as xenoestrogenic compounds (including alkylphenols and bisphenol A), can act via nongenomic signaling initiated by liganding of the plasma membrane estrogen receptor-α (mERα). We examined heterotrimeric G protein involvement leading to extracellular-regulated kinase (ERK) activation in GH3/B6/F10 rat anterior pituitary tumor cells that express abundant mERα, and smaller amounts of mERβ and GPR30. A combination of microarrays, immunoblots, and quantitative immunoassays demonstrated the expression of members of all α, β, and γ G protein classes in these cells. Use of selective inhibitors showed that the Gαi subtype was the primary initiator of downstream ERK signaling. Using antibodies against the GTP-bound form of Gα protein subtypes i and s, we showed that xenoestrogens (bisphenol A, nonylphenol) activated Gαi at 15-30 sec; all alkylphenols examined subsequently suppressed activation by 5 min. GTP-activation of Gαi for all estrogens was enhanced by irreversible cumulative binding to GTPγS. In contrast, Gαs was neither activated nor deactivated by these treatments with estrogens. ERα and Gαi co-localized outside nuclei and could be immuno-captured together. Interactions of ERα with Gαi and caveolin I were demonstrated by epitope proximity ligation assays. An ERα/β antagonist (ICI182780) and a selective disruptor of caveolar structures (nystatin) blocked estrogen-induced ERK activation. Conclusions Xenoestrogens, like physiologic estrogens, can evoke downstream kinase signaling involving selective interactions of ERα with Gαi and caveolin I, but with some different characteristics, which could explain their disruptive actions.

Localisation and endocrine control of hyaluronan synthase (HAS) 2, HAS3 and CD44 expression in sheep granulosa cells

“…For example, E2 stimulates many intracellular cascades involving phosphatidylinositol 3-kinase and mitogen-activated protein kinase (MAPK). Conversely, MAPKs affect steroidogenesis by regulating steroidogenic acute regulatory protein (StAR) expression (Moriarty et al 2006;Watson et al 2012;Manna and Stocco 2011). Similarly, the presence of gonadotropins (FSH or LH) plus E2 enhanced both HAS2 and HAS3 expression in our cultures.…”

International Union of Basic and Clinical Pharmacology. XCVII. G Protein–Coupled Estrogen Receptor and Its Pharmacologic Modulators

“…Consumer products including detergents, surfactants, resins, lubricants, plasticizers, fire retardants, and pesticides have been identified as sources of xenoestrogens, and scrutiny has focused on chemical classes such as alkyl phenols and esters of parahydroxybenzoic acid, phthalates, polybrominated diphenyl ethers, organophosphates, chlorinated hydrocarbons, and biphenyls (Shanle and Xu, 2011). Although many xenoestrogens exhibit low binding affinities to the nuclear ERs and often require relatively high concentrations ($1 mM) to affect genomic pathways, recent studies have focused on xenoestrogen effects on rapid nongenomic signaling pathways where significantly more potent, low-dose effects have been observed, including those that involve GPER-mediated processes (Thomas and Dong, 2006;Shanle and Xu, 2011;Marino et al, 2012;Watson et al, 2012Watson et al, , 2014.…”

Membrane Glucocorticoid Receptor Activation Induces Proteomic Changes Aligning with Classical Glucocorticoid Effects

“…For example, GC stimulation of a lung cell line led to the activation of protein kinase B (PKB) in a Caveolin-dependent mechanism (30). Similarly the presence of Cav-1 and G-protein was required for membrane estrogen receptor (34) and membrane androgen receptor activation (35), suggesting that Cav-1 and probably the associated lipid rafts, may play a role in steroid membrane signaling.…”