Estrogen induces estrogen-related receptor alpha gene expression and chromatin structural changes in estrogen receptor (ER)-positive and ER-negative breast cancer cells

Estrogen-related receptor alpha (ERRalpha), a member of the nuclear receptor superfamily, is closely related to the estrogen receptors (ERalpha and ERbeta). The ERRalpha gene is estrogen-responsive in several mouse tissues and cell lines, and a multiple hormone-response element (MHRE) in the promoter is an important regulatory region for estrogen-induced ERRalpha gene expression. ERRalpha was recently shown to be a negative prognostic factor for breast cancer survival, with its expression being highest in cancer cells lacking functional ERalpha. The contribution of ERRalpha in breast cancer progression remains unknown but may have important clinical implications. In this study, we investigated ERRalpha gene expression and chromatin structural changes under the influence of 17beta-estradiol in both ER-positive MCF-7 and ER-negative SKBR3 breast cancer cells. We mapped the nucleosome positions of the ERRalpha promoter around the MHRE region and found that the MHRE resides within a single nucleosome. Local chromatin structure of the MHRE exhibited increased restriction enzyme hypersensitivity and enhanced histone H3 and H4 acetylation upon estrogen treatment. Interestingly, estrogen-induced chromatin structural changes could be repressed by estrogen antagonist ICI 182 780 in MCF-7 cells yet were enhanced in SKBR3 cells. We demonstrated, using chromatin immunoprecipitation assays, that 17beta-estradiol induces ERRalpha gene expression in MCF-7 cells through active recruitment of co-activators and release of co-repressors when ERRalpha and AP1 bind and ERalpha is tethered to the MHRE. We also found that this estrogen effect requires the MAPK signaling pathway in both cell lines.     

Estrogen-related receptors-stimulated monoamine oxidase B promoter activity is down-regulated by estrogen receptors

Although there are studies published about the neuroprotective effect of estrogen, little is known about the mechanisms and cellular targets of the hormone. Recent reports demonstrate that estrogen down-regulates the expression of monoamine oxidase A and B (MAO-A and MAO-B) in the hypothalamus of the Macaques monkey, both of which are key isoenzymes in the neurotransmitter degradation pathway. Additionally, estrogen-related receptor alpha (ERRalpha) up-regulates MAO-B gene expression in breast cancer cells. ERRalpha recognizes a variety of estrogen response elements and shares many target genes and coactivators with estrogen receptor alpha (ERalpha). In this study, we investigate the interplay of ERs and ERRs in the regulation of MAO-B promoter activity. We demonstrate that ERRalpha and ERRgamma up-regulate MAO-B gene activity, whereas ERalpha and ERbeta decrease stimulation in both a ligand-dependent and -independent manner. Ectopically expressed ERRalpha and ERRgamma stimulate the expression of MAO-B mRNA and protein as well as increase the MAO-B enzymatic activity in ER-negative HeLa cells. The ability of ERRs to stimulate MAO-B promoter activity was reduced in ER-positive MCF-7 and T47D cells. Several AGGTCA motifs of the MAO-B promoter are responsible for up-regulation by ERRs. Interestingly, ERalpha or ERbeta alone have no effect on MAO-B promoter activity but can down-regulate the activation function of ERRs, whereas glucocorticoid receptor does not. By using chromatin immunoprecipitation assay, we demonstrate that ERs compete with ERRs for binding to the MAO-B promoter at selective AGGTCA motifs, thereby changing the chromatin status and cofactor recruitment to a repressed state. These studies provide new insight into the relationship between ERalpha, ERbeta, ERRalpha, and ERRgamma in modulation of MAO-B gene activity.     

Estrogen-related receptor alpha (ERRalpha) is a transcriptional regulator of apolipoprotein A-IV and controls lipid handling in the intestine

The estrogen-related receptor alpha (ERRalpha) is an orphan member of the superfamily of nuclear receptors involved in the control of energy metabolism. In particular, ERRalpha induces a high energy expenditure in the presence of the coactivator PGC-1alpha. However, ERRalpha knockout mice have reduced fat mass and are resistant to diet-induced obesity. ERRalpha is expressed in epithelial cells of the small intestine, and because the intestine is the first step in the energy chain, we investigated whether ERRalpha plays a function in dietary energy handling. Gene expression profiling in the intestine identified a subset of genes involved in oxidative phosphorylation that were down-regulated in the absence of ERRalpha. In support of the physiological role of ERRalpha in this pathway, isolated enterocytes from ERRalpha knockout mice display lower capacity for beta-oxidation. Microarray results also show altered expression of genes involved in dietary lipid digestion and absorption, such as pancreatic lipase-related protein 2 (PLRP2), fatty acid-binding protein 1 and 2 (L-FABP and I-FABP), and apolipoprotein A-IV (apoA-IV). In agreement, we found that ERRalpha-/- pups exhibit significant lipid malabsorption. We further show that the apoA-IV promoter is a direct target of ERRalpha and that its presence is required to maintain basal level but not feeding-induced regulation of the apoA-IV gene in mice. ERRalpha, in cooperation with PGC-1alpha, activates the apoA-IV promoter via interaction with the apoC-III enhancer in both human and mouse. Our results demonstrate that apoA-IV is a direct ERRalpha target gene and suggest a function for ERRalpha in intestinal fat transport, a crucial step in energy balance.     

The orphan nuclear receptor SHP regulates PGC-1alpha expression and energy production in brown adipocytes

Brown adipocytes increase energy production in response to induction of PGC-1alpha, a dominant regulator of energy metabolism. We have found that the orphan nuclear receptor SHP (NR0B2) is a negative regulator of PGC-1alpha expression in brown adipocytes. Mice lacking SHP show increased basal expression of PGC-1alpha, increased energy expenditure, and resistance to diet-induced obesity. Increased PGC-1alpha expression in SHP null brown adipose tissue is not due to beta-adrenergic activation, since it is also observed in primary cultures of SHP(-/-) brown adipocytes that are not exposed to such stimuli. In addition, acute inhibition of SHP expression in cultured wild-type brown adipocytes increases basal PGC-1alpha expression, and SHP overexpression in SHP null brown adipocytes decreases it. The orphan nuclear receptor ERRgamma is expressed in BAT and its transactivation of the PGC-1alpha promoter is potently inhibited by SHP. We conclude that SHP functions as a negative regulator of energy production in BAT.