Estradiol Rapidly Regulates Membrane Estrogen Receptor α Levels in Hypothalamic Neurons

Abstract

Estrogen receptors (ERs) and estrogen-binding proteins have been localized intracellularly and on the cell surface. The membraneassociated proteins initiate signaling that activates a myriad of cellular responses including the modulation of ion channels and ultimately transcription. Although many of the downstream actions of membrane ERs, including ER␣ and ER␤, have been characterized, the mechanisms regulating membrane ER levels have remained elusive in the nervous system. In the present study, we used surface biotinylation to identify and study the estradiol regulation of membrane ER␣ in mixed-sex, cultured hypothalamic neurons from rat. Following surface biotinylation, Western blot analysis revealed full-length 66 kDa ER␣ and several ER␣ splice variants, most notably a biotinylated 52 kDa ER␣-immunoreactive protein. Treatment of the neurons with estradiol caused a rapid and transient increase of the biotinylated 52 kDa and 66 kDa ER␣ proteins in the plasma membrane. Exposure of the neurons to estradiol also significantly increased internalization of 52 kDa and 66 kDa ER␣ membrane proteins, a measure of receptor activation. In the hypothalamus, membrane ER␣ signaling depends on transactivation of metabotropic glutamate receptor-1a (mGluR1a). Estradiol treatment increased the internalization of mGluR1a in parallel with ER␣, a finding consistent with the hypothesis of an ER␣-mGluR1a signaling unit. These results demonstrate that estradiol regulates the amount of ER␣ in the membrane, suggesting estradiol can regulate its own membrane signaling.

Insights into Rapid Modulation of Neuroplasticity by Brain Estrogens

“…The possibility of surfaceexpressing receptors has also been suggested by various biochemical studies. Using surface biotinylation assays, Dominguez and Micevych (2010) demonstrated the surface expression of ERa and potential splice variants in mixed sex hypothalamic cultures, supporting evidence from reports using conjugated 17b-estradiol that ERs are expressed on the surface.…”

Localization of Estrogen Receptor in the Central Lymphoid Organs of Chickens during the Late Stage of Embryogenesis

“…Recently, ER was reported to be present on the plasma membrane of various cell types of other systems, including the central nervous system and the blood vascular system. [18][19][20] In the case of immune cells, the intracellular calcium concentrations of T cells and macrophages increased rapidly after estradiol treatment, indicating that the presence of ER on the plasma membrane in these cells. [26][27][28] However, it has been reported that ER was not present on the plasma membrane in mouse Bcells.…”

“…Recently, expression of functional ER on the membrane was detected in various immune cells in mammals. [18][19][20] The membrane ER has been reported to have functions different from those of nuclear ER, which is traditionally known as the receptor of estrogen.…”

Subcellular Mechanisms in Pulmonary Arterial Hypertension: Combinatorial Modalities that Inhibit Anterograde Trafficking and Cause Bone Morphogenetic Protein Receptor Type 2 Mislocalization

“…In light of recent reports highlighting the effects of E2 on plasma membrane and ER functions in a nongenomic manner [28][29][30][31][32] and the known responsiveness of STAT5a/b proteins to E2, 23 we investigated whether exposure of endothelial cells to E2 with or without additional knockdown of STAT5a/b might affect the subcellular localization of wt BMPR2. The data in Figure 9A and 9B first confirm the effect of STAT5a/b knockdown in causing increased intracellular trapping of wt BMPR2.…”

“…27 Moreover, STAT5 species are already recognized to mediate aspects of the sexual dimorphic phenotypes in terms of postpubertal development and gene expression. 22,23 Additionally, the known responsiveness of STAT5a/b to E2 23 and the newly recognized nongenomic effects of E2 on ER membranes itself [28][29][30][31][32] made it attractive to investigate the effects of these combinatorial modalities (STAT5a/b downregulation and E2) on trafficking of BMPR2.…”