Forskolin Stimulates Estrogen Receptor (ER) Transcriptional Activity and Protects ER from Degradation by Distinct Mechanisms.

Estradiol action is mediated by estrogen receptors (ERs), and . Estradiol binding initiates ER-mediated transcription and ER degradation, the latter of which occurs via the ubiquitin-proteasome pathway. Inhibition of proteasome activity prevents estradiol-induced ER degradation and transactivation.

Women at extreme risk for obesity-related carcinogenesis: Baseline endometrial pathology and impact of bariatric surgery on weight, metabolic profiles and quality of life.

Objectives: The study objectives were to determine baseline endometrial histology in morbidly obese women undergoing bariatric surgery and to assess the surgical intervention's impact on serum metabolic parameters, quality of life (QOL), and weight.

Methods: Women undergoing bariatric surgery were enrolled. Demographic and clinicopathologic data, serum, and endometrium (if no prior hysterectomy) were collected preoperatively and serum collected postoperatively.

A new role for wilms tumor protein 1: differential activities of + KTS and -KTS variants to regulate LHβ transcription.

Luteinizing hormone (LH) is synthesized and secreted throughout the reproductive cycle from gonadotrope cells in the anterior pituitary, and is required for steroidogenesis and ovulation. LH contains an α-subunit common with FSH, and a unique LHβ subunit that defines biological activity. Basal LHβ transcription is low and stimulated by hypothalamic GnRH, which induces synthesis of early growth response protein-1 (Egr1), and stimulates binding of transcription factors Egr1 and steroidogenic factor-1 (SF1) on the promoter.

Estrogen modulation of endosome-associated toll-like receptor 8: an IFNα-independent mechanism of sex-bias in systemic lupus erythematosus.

Females of child-bearing age are more resistant to infectious disease and have an increased risk of systemic lupus erythematosus (SLE). We hypothesized that estrogen-induced gene expression could establish an immunoactivated state which would render enhanced defense against infection, but may be deleterious in autoimmune development. Using peripheral blood mononuclear cells (PBMCs), we demonstrate enhanced responses with immunogen stimulation in the presence of 17β-estradiol (E2) and gene array analyses reveal toll-like receptor 8 (TLR8) as an E2-responsive candidate gene.

AMP-activated protein kinase is a key intermediary in GnRH-stimulated LHβ gene transcription.

GnRH regulation of pituitary gonadotropin gene transcription is critical for fertility, and metabolic dysregulation is associated with reproductive disorders and altered hypothalamic-pituitary responses. Here, we examined signaling pathways in gonadotropes through which GnRH modulates gonadotropin levels, and potential common signaling pathways with insulin. Using LβT2 cells, we show that GnRH rapidly (5 minutes) triggers activating phosphorylation of AMP-activated protein kinase (AMPK) up to 5-fold; this stimulation is enhanced by insulin through increased total AMPKα levels and activity.

Introduction to the year in basic science series...2009.

This year represents the second, of what we expect to be an annual series, of articles based on The Endocrine Society annual meeting presentations that highlight recent advances in vibrant basic science areas in endocrinology. For ENDO 09, two general areas with broad appeal and significance to our members were chosen: neuroendocrinology and G protein-coupled receptors. The invited participants were charged with presenting and discussing important papers that were published approximately during the year leading up to the most recent annual meetings (June 2009) and to put them into broad perspective for the greater endocrine community.

Differential regulation of gonadotropin-releasing hormone neuron activity and membrane properties by acutely applied estradiol: dependence on dose and estrogen receptor subtype.

Gonadotropin-releasing hormone (GnRH) neurons are critical to controlling fertility. In vivo, estradiol can inhibit or stimulate GnRH release depending on concentration and physiological state. We examined rapid, nongenomic effects of estradiol.

Proteasome regulation of dynamic transcription factor occupancy on the GnRH-stimulated luteinizing hormone beta-subunit promoter.

GnRH is the main modulator of LH secretion and transcription of the LH subunit genes in pituitary gonadotropes. The LHbeta gene is preferentially transcribed during pulsatile GnRH stimuli of one pulse/30 min and is thus carefully controlled by specific signaling pathways and transcription factors. We now show that GnRH-stimulated LHbeta transcription is also influenced by the ubiquitin-proteasome system.

Novel actions of estrogen to promote proliferation: integration of cytoplasmic and nuclear pathways.

Both steroids and growth factors stimulate proliferation of steroid-dependent tumor cells, and interaction between these signaling pathways occurs at several levels. Steroid receptors are classified as ligand-activated transcription factors, and steps by which they activate target gene transcription are well understood. Several steroid responses have now been functionally linked to other intracellular signaling pathways, including c-Src or tyrosine kinase receptors.

Introduction to The Year in Basic Science series.

This year, in response to member input and suggestions to highlight the vibrant basic science of endocrinology, The Endocrine Society Annual Meeting (ENDO 08) introduced a new feature, The Year in Basic Science series. Among the many interests and strengths of our members, three broad areas were chosen for initial consideration: nuclear receptors, kinase signaling, and hormones and cancer. Speakers were invited to present and discuss important publications during the past year between annual meetings (roughly June to June), and to put these findings into broad perspective for the endocrine community.

Signal transducer and activator of transcription 5b, c-Src, and epidermal growth factor receptor signaling play integral roles in estrogen-stimulated proliferation of estrogen receptor-positive breast cancer cells.

17beta-Estradiol (E2) acts through the estrogen receptor alpha (ERalpha) to stimulate breast cancer proliferation. Here, we investigated the functional relationship between ERalpha and signal transducer and activator of transcription (STAT)5b activity in ER+ MCF-7 and T47D human breast cancer cells after specific knockdown of STAT5b. STAT5b small interfering RNA (siRNA) inhibited E2-induced bromodeoxyuridine (BrdU) incorporation in both cell lines, as well as the E2-induced increase in MCF-7 cell number, cyclin D1 and c-myc mRNA, and cyclin D1 protein expression, indicating that STAT5b is required for E2-stimulated breast cancer proliferation.

ERbeta in breast cancer--onlooker, passive player, or active protector?

The role of estrogen exposure in breast cancer risk is well-documented, and both estrogen synthesis and actions through the estrogen receptor (ER) have been targeted by therapies to control hormone-dependent breast cancer. The discovery of a second ER form and its therapeutic implications sparked great interest. Both the original ERalpha and the more recently identified ERbeta subtypes bind and respond similarly to many physiological and pharmacological ligands.

Estrogen enhances gonadotropin-releasing hormone-stimulated transcription of the luteinizing hormone subunit promoters via altered expression of stimulatory and suppressive transcription factors.

Transcription of the LH subunit genes is stimulated by GnRH and may be modulated physiologically by steroids such as 17beta-estradiol (E). We found that E treatment amplified GnRH stimulation of the rat LHbeta and alpha-subunit promoters, and expression of the endogenous mRNA, in LbetaT2 gonadotrope cells 2- to 5-fold above GnRH alone. We examined gene expression in LbetaT2 cells after E and/or GnRH treatment, and found that E suppressed expression of transcription factor Zfhx1a, and enhanced GnRH stimulation of Egr-1 mRNA and protein.

Luteinizing hormone beta promoter stimulation by adenylyl cyclase and cooperation with gonadotropin-releasing hormone 1 in transgenic mice and LBetaT2 Cells.

Rat luteinizing hormone beta (Lhb) gene transcription is stimulated by hypothalamic gonadotropin-releasing hormone 1 (GnRH1), and this response may be modulated by other signaling pathways such as cAMP. Here we characterize the ability of cAMP, alone or with GnRH1, to stimulate Lhb gene transcription in mouse pituitary and clonal gonadotroph cells. Both cAMP and pituitary adenylyl cyclase-activating peptide increase GnRH1 stimulation of luciferase activity in pituitaries of mice expressing the rat Lhb-luciferase transgene, suggesting cAMP and GnRH1 pathways interact in vivo.

Estrogen receptor-beta: why may it influence clinical outcome in estrogen receptor-alpha positive breast cancer?

In the previous issue of the journal, Lin and coworkers present data demonstrate that increased expression of estrogen receptor (ER)-beta in ER-alpha-positive breast cancer cells antagonizes a defined group of ER-alpha/estrogen stimulated genes that are involved in cell cycle regulation and DNA replication. Similar expression patterns for these genes were found human ER-alpha positive breast tumors expressing higher levels or ER-beta, and this correlated with better clinical outcome. The implications for these data, which suggest that ER-beta is a positive actor and diagnostic marker for therapeutic outcome, are discussed.

Integration of steroid and growth factor pathways in breast cancer: focus on signal transducers and activators of transcription and their potential role in resistance.

The signaling pathways that are critical to the development and growth of breast cancer include those activated downstream of the estrogen receptor (ER) and the human epidermal growth factor receptor family. Many of these pathways, including the signal transducer and activator of transcription pathway, are common to both. The well-described genomic actions of ER involve its role as a transcription factor, either by binding directly to DNA through estrogen response elements, or by tethering to DNA through interaction with other proteins.

Physical and functional interactions between Cas and c-Src induce tamoxifen resistance of breast cancer cells through pathways involving epidermal growth factor receptor and signal transducer and activator of transcription 5b.

High expression of the adaptor molecule Cas has been linked to resistance to the antiestrogen tamoxifen, both in tissue culture and in human tumors. The aim of this study was to elucidate the mechanism(s) by which overexpression of Cas confers resistance to tamoxifen. Cas overexpression in MCF-7 breast cancer cells was shown to alleviate both tamoxifen-mediated growth inhibition and induction of apoptosis.

Mechanisms for pulsatile regulation of the gonadotropin subunit genes by GNRH1.

The frequency of gonadotropin-releasing hormone (GNRH1, or GnRH) pulses secreted from the hypothalamus determine the ratios of the gonadotropin subunit genes luteinizing hormone beta (Lhb), follicle-stimulating hormone beta (Fshb) and the common alpha-glycoprotein subunit gene (Cga) transcribed in the anterior pituitaries of mammals. Fshb is preferentially transcribed at slower GNRH1 pulse frequencies, whereas Lhb and Cga are preferentially transcribed at more rapid pulse frequencies. Producing the gonadotropins in the correct proportions is critical for normal fertility.

Stimulation of the novel estrogen receptor-alpha intronic TERP-1 promoter by estrogens, androgen, pituitary adenylate cyclase-activating peptide, and forskolin, and autoregulation by TERP-1 protein.

The estrogen receptor-alpha (ERalpha) pituitary-specific variant, TERP-1, is regulated dramatically by physiological status. We examined hormonal regulation of the TERP-1 promoter in transient transfection assays in GH3 somatolactotrope cells. We found that 17beta-estradiol (E2), genistein, androgen, pituitary adenylate cyclase-activating peptide, and forskolin (FSK) all stimulated TERP-1 promoter activity, whereas progesterone had no effect.

Estrogen negatively regulates epidermal growth factor (EGF)-mediated signal transducer and activator of transcription 5 signaling in human EGF family receptor-overexpressing breast cancer cells.

Breast cancer cell growth may be stimulated by 17beta-estradiol (E2) or growth factors like epidermal growth factor (EGF). However, tumors typically depend on only one of these pathways and may overexpress either estrogen receptor (ER) or EGF receptor (EGFR) and related family members. Tumors overexpressing EGFR are more aggressive than those expressing ER.

The estrogen receptor (ER)alpha variant Delta5 exhibits dominant positive activity on ER-regulated promoters in endometrial carcinoma cells.

Estrogen receptor (ER)alpha is a ligand-inducible transcription factor that mediates the physiological effects of 17beta-estradiol (E2). In the uterus, E2 is involved in tissue growth, maintenance, and differentiation. Delta5ERalpha (Delta5) is an ERalpha variant protein expressed in uterine tumors but not in normal tissue.

Crosstalk between steroid receptors and the c-Src-receptor tyrosine kinase pathways: implications for cell proliferation.

Both steroids and growth factors stimulate proliferation of steroid-dependent tumor cells, and interaction between these signaling pathways may occur at several levels. Steroid receptors are typically classified as ligand-activated transcription factors, and steps by which they bind ligand, dimerize, recruit coregulatory molecules, and activate target gene transcription are well understood. Several steroid responses are functionally linked to c-Src or tyrosine kinase receptors, and the physiological impact and the precise molecular pathways involved in these responses are under intensive investigation.

Thyrotropin-releasing hormone-stimulated thyrotropin expression involves islet-brain-1/c-Jun N-terminal kinase interacting protein-1.

Islet-brain-1 (IB1)/c-Jun N-terminal kinase interacting protein 1 (JIP-1) is a scaffold protein that is expressed at high levels in neurons and the endocrine pancreas. IB1/JIP-1 interacts with the c-Jun N-terminal kinase and mediates the specific physiological stimuli (such as cytokines). However, the potential role of the protein in the pituitary has not been evaluated.

Role of calcium-calmodulin-dependent protein kinase cascade in thyrotropin (TSH)-releasing hormone induction of TSH and prolactin gene expression.

TRH binds to a membrane receptor that activates several intracellular signaling pathways and increases transcription of the TSH and prolactin (PRL) genes. Although TRH induces TSH and PRL gene expression, the underlying mechanism is not clear. In this report we examined the role of the Ca(2+)/calmodulin-dependent protein (CaM) kinase cascade in mediating TRH-stimulated transcription of TSH and PRL.

Protein kinase A activation of estrogen receptor alpha transcription does not require proteasome activity and protects the receptor from ligand-mediated degradation.

17beta-Estradiol (E2)-stimulated estrogen receptor (ERalpha) transcription is accompanied by protein degradation via the 26S-proteasome pathway. Inhibition of proteasome activity stabilizes ERalpha protein and abolishes E2-activated transcription, suggesting functional linkages between transcription and degradation. It is not known whether ligand-independent ERalpha activation is coupled to proteolysis.