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Haem is an essential prosthetic group of numerous proteins and a central signalling molecule in many physiologic processes.sup.1,2. The chemical reactivity of haem means that a network of intracellular chaperone proteins is required to avert the cytotoxic effects of free haem, but the constituents of such trafficking pathways are unknown.sup.3,4. Haem synthesis is completed in mitochondria, with ferrochelatase adding iron to protoporphyrin IX. How this vital but highly reactive metabolite is delivered from mitochondria to haemoproteins throughout the cell remains poorly defined.sup.3,4. Here we show that progesterone receptor membrane component 2 (PGRMC2) is required for delivery of labile, or signalling haem, to the nucleus. Deletion of PGMRC2 in brown fat, which has a high demand for haem, reduced labile haem in the nucleus and increased stability of the haem-responsive transcriptional repressors Rev-Erb[alpha] and BACH1. Ensuing alterations in gene expression caused severe mitochondrial defects that rendered adipose-specific PGRMC2-null mice unable to activate adaptive thermogenesis and prone to greater metabolic deterioration when fed a high-fat diet. By contrast, obese-diabetic mice treated with a small-molecule PGRMC2 activator showed substantial improvement of diabetic features. These studies uncover a role for PGRMC2 in intracellular haem transport, reveal the influence of adipose tissue haem dynamics on physiology and suggest that modulation of PGRMC2 may revert obesity-linked defects in adipocytes. Progesterone receptor membrane component 2 is required to transport haem from the mitochondria to the nucleus, where, in adipose tissue, it has roles in regulation of thermogenesis and glucose metabolism., Author(s): Andrea Galmozzi [sup.1] , Bernard P. Kok [sup.1] , Arthur S. Kim [sup.1] , J. Rafael Montenegro-Burke [sup.2] , Jae Y. Lee [sup.1] , Roberto Spreafico [sup.3] , Sarah [...]

Progesterone receptor (PR) expression is used as a biomarker of oestrogen receptor-[alpha] (ER[alpha]) function and breast cancer prognosis. Here we show that PR is not merely an ER[alpha]-induced gene target, but is also an ER[alpha]-associated protein that modulates its behaviour. In the presence of agonist ligands, PR associates with ER[alpha] to direct ER[alpha] chromatin binding events within breast cancer cells, resulting in a unique gene expression programme that is associated with good clinical outcome. Progesterone inhibited oestrogen-mediated growth of ER[alpha].sup.+ cell line xenografts and primary ER[alpha].sup.+ breast tumour explants, and had increased anti-proliferative effects when coupled with an ER[alpha] antagonist. Copy number loss of PGR, the gene coding for PR, is a common feature in ER[alpha].sup.+ breast cancers, explaining lower PR levels in a subset of cases. Our findings indicate that PR functions as a molecular rheostat to control ER[alpha] chromatin binding and transcriptional activity, which has important implications for prognosis and therapeutic interventions. Progesterones, oestrogens and their receptors (PR, ER[alpha] and ER[beta]) are essential in normal breast development and homeostasis, as well as in breast cancer; here it is shown that PR controls ER[alpha] function by redirecting where ER[alpha] binds to the chromatin, acting as a proliferative brake in ER[alpha].sup.+ breast tumours. Steroid receptor crosstalk in breast cancer Progesterones and their receptor (PR) and oestrogens and their receptors (ER[alpha] and ER[beta]) play crucial roles in normal breast development and homeostasis, as well as in breast cancer, where the presence of these receptors has been used as a prognostic marker of whether breast cancers will respond to ER receptor antagonists. The relationship between their functions has not been entirely clear, and now Jason Carroll and colleagues reveal a key piece of the puzzle by showing that the PR controls ER[alpha] function. By re-directing where ER[alpha] binds to chromatin, it acts as a proliferative brake in ER[alpha].sup.+ breast tumours. Accordingly, loss of the PGR gene, which encodes the PR, is associated with poorer outcome in breast cancer patients., Author(s): Hisham Mohammed [sup.1] , I. Alasdair Russell [sup.1] , Rory Stark [sup.1] , Oscar M. Rueda [sup.1] , Theresa E. Hickey [sup.2] , Gerard A. Tarulli [sup.2] , Aurelien [...]

ABSTRACT Progesterone is an important sex steroid that plays a vital role during ovarian development in crustaceans. In vertebrates, progesterone mediates reproduction via the progesterone receptor (PR). Previous studies have [...]

Background/Objectives: There is few data on the association between dietary fiber intake and estrogen receptor (ER)/ progesterone receptor (PR)-defined breast cancer risk. The present study aimed to investigate the associations between total dietary fiber and dietary fiber fractions intake and breast cancer risk by ER and PR status in a hospital-based case- control study among Chinese women. Subjects/Methods: Four hundred and thirty-eight cases with primary breast cancer were consecutively recruited from June 2007 to August 2008 and frequency matched to 438 controls by age (5-year interval) and residence (rural/urban). A validated food frequency questionnaire was used to assess the dietary intake through a face-to-face interview. Unconditional logistic regression models were used to estimate odds ratios (ORs) and 95% confidence interval (CI) after adjusting for various potential confounders. Results: A statistically significant inverse association was found between total dietary fiber and fiber fractions intake and breast cancer risk. The adjusted ORs (95% CIs) for the highest versus the lowest quartile of intake were 0.31 (0.20-0.47) for total dietary fiber, 0.73 (0.48-1.11) for soy fiber, 0.48 (0.22-0.97) for vegetable fiber and 0.54 (0.31-0.92) for fruit fiber. No association was observed for cereal fiber intake and risk. An inverse association between dietary fiber intake and breast cancer risk was observed in ER+ ,ER-,PR+ ,ER+ PR+ and ER-PR+ tumors. Conclusions: Our results suggest that consumption of total dietary fiber and fiber from vegetable and fruit was inversely associated with breast cancer risk. These inverse associations were more prominent in some subtypes of ER and PR breast cancers. European journal of Clinical Nutrition (2011) 65, 929-936; doi:10.1038/ejcn.2011.57; published online 4 May 2011 Keywords: fiber; breast cancer; estrogen receptor; progesterone receptor, Introduction Diets high in fiber have been hypothesized to protect against breast cancer through a number of mechanisms, including increasing excretion of estrogens, inhibition of intestinal estrogen reabsorption by affecting [...]

Epithelial-specific activation of the PI3-kinase pathway is the most common genetic alteration in type I endometrial cancer. In the majority of these tumors, PTEN expression is lost in the epithelium but maintained in tumor stroma. Currently reported PTEN knockout mouse models initiate type I endometrial cancer concomitant with loss of PTEN in both uterine epithelium and stroma. Consequently, the biologic outcome of selectively activating the PI3-kinase pathway in the endometrial epithelium remains unknown. To address this question, we established a malleable in vivo endometrial regeneration system from dissociated murine uterine epithelium and stroma. Regenerated endometrial glands responded to pharmacologic variations in hormonal milieu similar to the native endometrium. Cell-autonomous activation of the PI3-kinase pathway via biallelic loss of PTEN or activation of AKT in adult uterine epithelia in this model was sufficient to initiate endometrial carcinoma. AKT-initiated tumors were serially transplantable, demonstrating permanent genetic changes in uterine epithelia. Immunohistochemistry confirmed loss of PTEN or activation of AKT in regenerated hyperplastic glands that were surrounded by wild-type stroma. We demonstrate that cell-autonomous activation of the PI3-kinase pathway is sufficient for the initiation of endometrial carcinoma in naive adult uterine epithelia. This in vivo model provides an ideal platform for testing the response of endometrial carcinoma to targeted therapy against this common genetic alteration. tissue regeneration model | progesterone receptor | uterine cancer doi/ 10.1073/pnas.1012548107

Steroids play fundamental roles regulating mammalian reproduction and development. Although sex steroids and their receptors are well characterized in vertebrates and several arthropod invertebrates, little is known about the hormones and receptors regulating reproduction in other invertebrate species. Evolutionary insights into ancient endocrine pathways can be gained by elucidating the hormones and receptors functioning in invertebrate reproduction. Using a combination of genomic analyses, receptor imaging, ligand identification, target elucidation, and exploration of function through receptor knockdown, we now show that comparable progesterone chemoreception exists in the invertebrate monogonont rotifer Brachionus manjavacas, suggesting an ancient origin of the signal transduction systems commonly associated with the development and integration of sexual behavior in mammals. receptor | imaging steroids doi/ 10.1073/pnas.1006074107

The slow transit time of the colon in t females with constipation is due to impairment of agonist-induced contraction. The impairment is associated with downregulation of G proteins that mediate contraction and upregulation of Gs proteins that mediate relaxation. These changes are caused by overexpression of progesterone (P4) receptors in the colon, rendering its muscle cells sensitive to physiological P4 concentrations. Downregulation of Gq/11 is mediated by P4 receptor B (PR-B). We examined whether upregulation of Gs proteins increased the inhibition of contraction and whether the increase is mediated by the P4 receptor A (PR-A). These studies were conducted in colon-isolated colon muscle cells from human control and slow-transit constipation (STC) females and from guinea pigs. Muscle cell contraction was induced by CCK-8. Inhibition of contraction was induced by vasoactive intestinal polypeptide (VIP), and 8'bromo-c'AMP (8B-c'AMP) G protein levels were determined by Western blot. VIP-induced inhibition of contraction was greater in muscle cells from STC and P4-treated muscle cells. There were no differences in the inhibition induced by 8B-c'AMP between muscle cells from STC and P4-treated controls. The increased VIP-induced inhibition of muscle cells treated with P4 was blocked by pretreatment with PR-A antibodies and unaffected by PR-B antibodies. These antibodies had no effect on 8B-c'AMP induced-inhibition. The P4 upregulation of Gs proteins was blocked by PR-A antibodies and unaffected by PR-B antibodies. Similar results were obtained in muscle cells from guinea pig colons. We concluded that P4 upregulation of Gs proteins increases VIP-induced inhibition of contraction mediated by PR-A. G proteins; vasoactive intestinal polypeptide doi:10.1152/ajpgi.00346.2009.

The association of the 2464G > A SNP found in the promoter region of the rabbit progesterone receptor gene with progesterone receptor (PR) expression was evaluated by Western blot analysis. This SNP was associated with 2 lines divergently selected for uterine capacity, the high line selected to increase uterine capacity and the low line selected to decrease uterine capacity. Two progesterone isoforms were obtained using a commercial monoclonal antibody: the PR-B isoform described previously in rabbits, and the PR-A isoform, not described previously in rabbits. The GG genotype, the genotype more frequent in the high line, showed less PR-B and PR-A expression than the AA genotype in the oviduct (GG/[AA.sub.PR-B] = 0.81 and GG/[AA.sub.PR-A] = 0.73) and uterus (around 0.70 in both isoforms). The GA genotype showed similar PR-A expression in both tissues and also similar PR-B expression in the oviduct to the GG genotype. Conversely, the GG genotype showed less PR-B expression than the GA genotype in the uterus (GG/[GA.sub.PR-B] = 0.79). Similar expression of both PR isoforms was found in the uterus at d 2 and 3 of gestation; meanwhile, an increase of both isoforms was observed in the oviduct. Similar PR-A expression was observed in the ampulla and isthmus; meanwhile, the PR-B expression in the isthmus was double that in the ampulla. Key words: oviduct, PGR genotype, progesterone receptor expression, rabbit, uterus doi: 10.2527/jas.2009-1955

Normal endometrial function requires a balance of progesterone (P4) and estrogen (E2) effects. An imbalance caused by increased E2 action and/or decreased P4 action can result in abnormal endometrial proliferation and, ultimately, endometrial adenocarcinoma, the fourth most common cancer in women. We have identified mitogen-inducible gene 6 (Mig-6) as a downstream target of progesterone receptor (PR) and steroid receptor coactivator (SRC-1) action in the uterus. Here, we demonstrate that absence of Mig-6 in mice results in the inability of P4 to inhibit E2-induced uterine weight gain and E2-responsive target genes expression. At 5 months of age, the absence of Mig-6 results in endometrial hyperplasia. Ovariectomized [Mig-6.sup.d/d] mice exhibit this hyperplastic phenotype in the presence of E2 and P4 but not without ovarian hormone. Ovariectomized [Mig-6.sup.d/d] mice treated with E2 developed invasive endometrioid-type endometrial adenocarcinoma. Importantly, the observation that endometrial carcinomas from women have a significant reduction in MIG-6 expression provides compelling support for an important growth regulatory role for Mig-6 in the uterus of both humans and mice. This demonstrates the Mig-6 is a critical regulator of the response of the endometrium to E2 in regulating tissue homeostasis. Since Mig-6 is regulated by both PR and SRC-1, this identifies a PR, SRC-1, Mig-6 regulatory pathway that is critical in the suppression of endometrial cancer. estrogen | endometrial cancer | progesterone | progesterone receptor | SRC-1

A total of 598 [F.sub.2] does from a cross between the high and low lines selected divergently for uterine capacity during 10 generations were used in a candidate gene analysis. The presence of major genes affecting the number of implanted embryos and uterine capacity has been suggested in lines divergently selected for uterine capacity. Uterine capacity is a main component of litter size. The progesterone receptor gene was tested as a candidate gene to determine whether polymorphisms explain differences in litter size and its components. Fragments of the promoter region and exons 1-8 were amplified and sequenced. One SNP was found in the promoter region, 2464G>A, three SNPs in the 5'-UTR exon 1, and a silence SNP in exon 7. The first four SNPs were segregated in two haplotypes. The allele G found in the promoter region was found in 75% of the high-line parental animals and in 29% of the low-line parental animals. The GG genotype had 0.5 kits and 0.5 implanted embryos more than the AA genotype. At 48 hr of gestation, the difference in early embryo survival and embryonic stage of development was small. However, at 72 hr of gestation, the GG genotype had 0.36 embryos more than the AA genotype and also had a more advanced embryonic stage of development, showing a lower percentage of compacted morulae and a higher percentage of blastocysts. The difference in litter size between the GG and GA genotypes was similar to the difference found between homozygote genotypes; however, differences in implanted embryos, early embryo survival, and embryo development were not detected between the GG and GA genotypes.

Results from epidemiological and experimental studies indicate that phytoestrogens may protect against breast cancer. Because one of the biological effects of phytoestrogens is probably estrogenic, it's possible that the preventive effect on breast cancer differs by estrogen receptor (ER) or progesterone receptor (PR) status of the tumor. We evaluated the associations between dietary phytoestrogen (isoflavonoids, lignans, and coumestrol) intake and risk of breast cancer and whether the ER/PR statuses of the tumor influence this relationship. In 1991-2 a prospective population-based cohort study among Swedish pre-and postmenopausal women was performed, making questionnaire data available for 45,448 women. A total of 1014 invasive breast cancers were diagnosed until December 2004. Cox proportional hazards models were performed to estimate multivariate risk ratios, 95% CI for associations with risk of breast cancer. Intakes of lignan, isoflavonoid, or coumestrol were not associated with breast cancer risk overall or before or after 50 y of age. The effects of lignans or isoflavonoids were independent of receptor status. However, intake of coumestrol was associated with decreased risk of receptor negative tumors (ER-PR-) but not positive tumors. The risk of ER-PR- tumors was significantly lower (50%) in women with intermediate coumestrol intake compared with those who did not consume any. In conclusion, we found no association between intake of isoflavonoids or lignans and breast cancer risk. Our results of a decreased risk of ER-PR- tumors in women with intermediate intake of coumestrol could be due to chance because of the low intake. The results should be confirmed in other studies.

There are two major subtypes of human breast cancers: the luminal, estrogen, and progesterone receptor-positive, cytokeratin 18-positive (E[R.sup+]P[R.sup+]CK[18.sup+]) subtype, and the basal E[R.sup-]P[R.sup-]CK[18.sup-]CK[5.sup+] subtype. Tumor-initiating cells (CD[44.sup+]) have been described for human breast cancers; whether these are common to the two subtypes is unknown. We have identified a rare population of cells that are both CD[44.sup+] and E[R.sup-]P[R.sup-]CK[5.sup+] in luminal-like E[R.sup+]P[R.sup+] T47D human breast tumor xenografts. The tumor-isolated CD[44.sup+] cell fraction was highly enriched for clonogenic (in vitro culture) and tumorigenic (in vivo reimplantation) cells compared with the CD[44.sup-] cell fraction. Rare E[R.sup-]P[R.sup-]CK[5.sup+] cells were present within CD[44.sup+]-derived colonies. Tumor-isolated cells placed in minimal media also contained rare E[R.sup-]P[R.sup-] CK[5.sup+] cells at early time points ( cancer stem cell | cytokeratin 5 | estrogen receptor | progesterone receptor

A recent clinical trial (Chwalisz K, Larsen L, Mattia-Goldberg C, Edmonds A, Elger W, Winkel CA. Fertil Steril 87: 1399-1412, 2007) has demonstrated that the selective progesterone receptor modulator asoprisnil efficiently causes the shrinkage of uterine leiomyoma. The present study was conducted to examine whether asoprisnil elicits endoplasmic reticulum (ER) stressinduced apoptosis in cultured human uterine leiomyoma cells. After subculture in phenol red-free DMEM supplemented with 10% FBS for 120 h, cultured cells were stepped down to serum-free conditions with or without graded concentrations of asoprisnil. ER stress-associated and apoptosis-related proteins were assessed by reverse transcription-PCR analysis or Western blot analysis. RNA interference of growth-arrest- and DNA-damage-inducible gene 153 (GADD153) was performed using small interfering RNA. Terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labeling (TUNEL)-positive rates were assessed by TUNEL assay. Compared with untreated control cultures, treatment with [10.sup.-7] M asoprisnil significantly (P < 0.05) increased the protein contents of ubiquitin at 2 h and phospho-double-stranded RNA-activated protein kinase-like ER kinase, phospho-eukaryotic initiation factor 2[alpha]. activating transcription factor 4, and glucose-regulated protein 78 kDa at 4 h, followed by the significant (P < 0.05) increase in GADD153 protein content at 6 h and cleaved poly(adenosine 5'-diphosphate ribose)polymerase (PARP) at 8 h. RNA interference of GADD153 suppressed protein contents of asoprisnil-induced cleaved PARP, Bax, Bak, GADD34, and tribbles-related protein 3 (TRB3) and TUNELpositive rate but attenuated asoprisnil-induced reduction in Bcl-2 protein content in cultured leiomyoma cells. These results suggest that asoprisnil elicits ER stress-induced apoptosis in cultured leiomyoma cells and that GADD153 plays a role in asoprisnil-induced apoptosis by modulating the Bcl-2 family of proteins, GADD34, and TRB3. growth-arrest- and DNA-damage-inducible gene 153; Bcl-2 family; tribbles-related protein-3; GADD34

We evaluated the role of estradiol and progesterone in allergic lung inflammation. Rats were ovariectomized (Ovx) and, 7 days later, were sensitized with ovalbumin (OA) and challenged after 2 wk with inhaled OA; experiments were performed 1 day thereafter. Ovx-allergic rats showed reduced cell recruitment into the bronchoalveolar lavage (BAL) fluid relative to sham-Ovx allergic rats, as was observed in intact allergic rats treated with ICI-182,780. Estradiol increased the number of ceils in the BAL of Ovx-allergic rats, whereas progesterone induced an additional reduction. Cells of BAL and bone marrow (BM) of Ovx-allergic rats released elevated amounts of IL-10 and reduced IL-1[beta] and TNF-[alpha] BM cells of Ovx-allergic rats released increased amounts of IL-10 and lower amounts of IL-4. Estradiol treatment of Ovx-allergic rats decreased the release of IL-10 but increased that of IL-4 by BM cells. Estradiol also caused an increased release of IL-1[beta] and TNF-[alpha] by BAL cells. Progesterone significantly increased the release of IL-10, IL-1[alpha], and TNF-[alpha] by BAL cells and augmented that of IL-4 by BM cells. Degranulation of bronchial mast cells from Ovx rats was reduced after in vitro challenge, an effect reverted by estradiol but not by progesterone. We suggest that the serum estradiol-to-progesterone ratio might drive cellular recruitment, modulating the pulmonary allergy and profile of release of anti-inflammatory or inflammatory cytokines. The existence of such dual hormonal effects suggests that the hormone therapy of asthmatic postmenopausal women and of those suffering of premenstrual asthma should take into account the possibility of worsening the pulmonary conditions. asthma; eosinophils

Human progesterone receptors (PR) exist as two functionally distinct isoforms, PR-A and PR-B. The proteins are identical except for an additional 164 residues located at the N terminus of PR-B. To determine the mechanisms responsible for isoform-specific functional differences, we present here a thermodynamic dissection of PR-A-promoter interactions and compare the results to our previous work on PR-B. This analysis has generated a number of results inconsistent with the traditional, biochemically based model of receptor function. Specifically, statistical models invoking preformed PR-A dimers as the active binding species demonstrate that intrinsic binding energetics are over an order of magnitude greater than is apparent. High-affinity binding is opposed, however, by a large energetic penalty. The consequences of this penalty are 2-fold: Successive monomer binding to a palindromic response element is thermodynamically favored over preformed dimer binding, and DNA-induced dimerization of the monomers is largely abolished. Furthermore, PR-A binding to multiple PREs is only weakly cooperative, as judged by a 5-fold increase in overall stability. Comparison of these results to our work on PR-B demonstrates that whereas both isoforms appear to have similar DNA binding affinities, PR-B in fact has a greatly increased intrinsic binding affinity and cooperative binding ability relative to PR-A. These differences thus suggest that residues unique to PR-B allosterically regulate the energetics of cooperative promoter assembly. From a functional perspective, the differences in microscopic affinities predict receptor--promoter occupancies that accurately correlate with the transcriptional activation profiles seen for each isoform. nuclear receptor | protein-DNA interactions | quantitative footprint titrations | statistical mechanics

The structure and structural properties of nuclear receptors is described focusing on the ligand-binding and DNA binding domains and unstructured N-terminal regions. To emphasize the allosteric interdependence among these subunits, a more detailed inspection of the structural properties of the human progesterone receptor is presented.

cAMP is required for differentiation of human endometrial stromal cells (HESCs) into decidual cells in response to progesterone, although the underlying mechanism is not well understood. We now demonstrate that cAMP signaling attenuates ligand-dependent sumoylation of the progesterone receptor (PR) in HESCs. In fact, decidualization is associated with global hyposumoylation and redistribution of small ubiquitin-like modifier (SUMO)-1 conjugates into distinct nuclear foci. This altered pattern of global sumoylation was not attributable to impaired maturation of SUMO-1 precursor or altered expression of E1 (SAE1/SEA2) or E2 (Ubc9) enzymes but coincided with profound changes in the expression of E3 ligases and SUMO-specific proteases. Down-regulation of several members of the protein inhibitors of activated STAT (PIAS) family upon decidualization pointed toward a role of these E3 ligases in PR sumoylation. We demonstrate that PIAS1 interacts with the PR and serves as its E3 SUMO ligase upon activation of the receptor. Furthermore, we show that silencing of PIAS1 not only enhances PR-dependent transcription but also induces expression of prolactin, a decidual marker gene, in progestin-treated HESCs without the need of simultaneous activation of the cAMP pathway. Our findings demonstrate how dynamic changes in the SUMO pathway mediated by cAMP signaling determine the endometrial response to progesterone. endometrium | protein inhibitor of activated STAT 1 | decidualization | progesterone receptor

Embryo implantation in the uterus is a critical step in mammalian reproduction, requiring preparation of the uterus receptive to blastocyst implantation. Uterine receptivity, also known as the window of implantation, lasts for a limited period, and it is during this period blastocysts normally implant. Ovarian steroid hormones estrogen and progesterone (P4) are the primary regulators of this process. The immunophilin FKBP52 serves as a cochaperone for steroid hormone nuclear receptors to govern appropriate hormone action in target tissues. Here we show a critical role for FKBP52 in mouse implantation. This immunophilin has unique spatiotemporal expression in the uterus during implantation, and females missing the Fkbp52 gene have complete implantation failure due to lack of attainment of uterine receptivity. The overlapping uterine expression of FKBP52 with nuclear progesterone receptor (PR) in wild-type mice together with reduced P4 binding to PR, attenuated PR transcriptional activity and down-regulation of several [P.sub.4]-regulated genes in uteri of Fkbp[52.sup.-/-] mice, establishes this cochaperone as a critical regulator of uterine P4 function. Interestingly, ovulation, another P4-mediated event, remains normal. Collectively, the present investigation provides evidence for an in vivo role for this cochaperone in regulating tissue-specific hormone action and its critical role in uterine receptivity for implantation. mouse | uterus | ovulation | blastocyst | progesterone receptor

A quantitative analysis of progesterone receptor (PR)-B self-association energetics is conducted. The studies highlight questions about the relative roles of monomer and dimer in PR-dependent biological function and may additionally offer insight into the mechanisms by which closely related steroid receptors generate transcriptional diversity.

Two forms of the classical progesterone receptors (PR), XPR-1 and XPR-2, have been cloned in Xenopus laevis. Their relative roles in mediating progesterone action in the ovaries are not clear. Using antibodies generated against the cloned XPR-2, we demonstrated here that the somatic follicle cells expressed an 80-kDa PR protein, termed XPR-1. Treatment of follicle cells with progesterone resulted in disappearance of this protein, consistent with proteosome-mediated XPR-1 protein degradation. A smaller (~70 kDa) PR protein, termed XPR-2, was expressed in the oocytes, but not in follicle cells. XPR-2 underwent progesterone-induced phosphorylation but not protein degradation. Treating isolated ovarian fragments with progesterone caused oocyte maturation and the release of the mature oocytes from the ovarian tissues ('ovulation'). Inhibition of transcription, with actinomycin D, did not interfere with progesterone-induced oocyte maturation but blocked 'ovulation' so that mature oocytes were trapped in the follicles. These results suggest that the dual functions of progesterone, transcription-dependent follicle rupture and transcription-independent oocyte maturation, are mediated by the two forms of PR proteins differentially expressed in the follicle cells and the oocytes, respectively. Keywords: Xenopus; Oocyte maturation; Ovulation; Progesterone receptor; Hyperphosphorylation; Protein degradation

Research has been conducted on the progesterone receptor high-affinity ligand, fluoro furanyl norprogesterone. The synthetic route developed for the synthesis of this ligand provides improvement in the yield of the fluoro furanyl norprogesterone.

Aim: To study the effects of tamoxifen on the proliferation index and oestrogen receptor (ER) and progesterone receptor (PR) expression in postmenopausal endometrium. Methods: A total of 125 endometrial specimens [...]

Mammary epithelium can functionally regenerate upon transplantation. This renewal capacity has been classically ascribed to the function of a multipotent mammary gland stem cell population, which has been hypothesized to be a primary target in the etiology of breast cancer. Several complementary approaches were employed in this study to identify and enrich mammary epithelial cells that retain stem cell characteristics. Using long-term BrdU labeling, a population of label retaining cells (LRCs) that lack expression of differentiation markers has been identified. LRCs isolated from mammary primary cultures were enriched for stem cell antigen-1 (Sca-1) and Hoechst dye-effluxing 'side population' properties. Sca-[1.sup.pos] cells in the mammary gland were localized to the luminal epithelia by using Sca-[1.sup.+/GFP] mice, were progesterone receptor-negative, and did not bind peanut lectin. Finally, the Sca-[1.sup.pos] population is enriched for functional stem/progenitor cells, as demonstrated by its increased regenerative potential compared with Sca-[1.sup.neg] cells when transplanted into the cleared mammary fat pads of host mice. Key Words: mammary; stem cells; BrdU; Sca-1; label retention; progesterone receptor.

The authors review the publications on nuclear receptor superfamily of transcription factors. The topics of interest include signal transduction mechanisms and the historical aspects of nuclear receptor research.

Author's Abstract: COPYRIGHT 1999, John Wiley & Sons, Inc. Fully grown Xenopus oocytes can remain in their immature state essentially indefinitely, or, in response to the steroid hormone progesterone, can be induced to develop intofertilizable eggs. This process is termed oocyte maturation. Oocyte maturation is initiated by a novel plasma membrane steroid hormone receptor. Progesterone brings about inhibition of adenylate cyclase and activation of the Mos/MEK1/p42 MAP kinase cascade, which ultimately brings about the activation of the universal M phase trigger Cdc2/cyclin B. Oocyte maturation provides an interesting example of how signaling cascades entrain the cell cycle clock to environmental changes.

Our understanding of the roles played by sex hormones in ovarian carcinogenesis has been limited by a lack of data concerning the mode of sex hormone action in human ovarian surface epithelial (HOSE) cells, the tissue of origin of >90% of ovarian cancers. We have compared the relative abundance of estrogen receptor (ER)[Alpha], ER[Beta], progesterone receptor (PR), and androgen receptor (AR) mRNA in four primary cultures of HOSE cells obtained from postmenopausal women to those found in late serous adenocarcinoma primary cell cultures and established ovarian cancer cell lines. We observed coexpression of ER[Alpha] and ER[Beta] mRNA along with AR and PR transcripts in normal HOSE cells and disruption of ERa mRNA expression as well as dramatic down-regulation of PR and AR transcript expression in most ovarian cancer cells. In contrast, levels of ER[Beta] mRNA were unaffected by the malignant state. Additionally, a novel mutation involving a 32-bp deletion in exon 1 of ER[Alpha] transcripts was detected in the SKOV3 cell line. This mutation would explain why SKOV3 was reported to be ER-positive but estrogen-insensitive. Taken together, these findings suggest that estrogens, signaling via either or both ER subtypes, may play an indispensable role in regulating normal HOSE cell functions. Therefore, loss of ERa, PR, and AR mRNA expression in HOSE cells may be responsible for neoplastic transformation in this cell type. In contrast, the roles played by ER[Beta] in normal and malignant HOSE cells remain elusive. Finally, the coexistence of mutated ERa mRNA and normal ER[Beta] transcripts in SKOV3 argues in favor of a dependency of ER[Beta] action on functional ER[Alpha]s.

Estrogen is known to increase progesterone receptor (PR) levels in the wild-type mouse uterus, and this estrogen induction was thought to be important for progesterone action through the PR. The estrogen receptor [Alpha] knockout (ERKO) mouse uterus was observed to express PR mRNA that cannot be induced by estrogen. Progesterone action was characterized to determine whether it was diminished in ERKO mice. The PR protein is present in the ERKO uterus at 60% of the level measured in a wild-type uterus. The PR-A and PR-B isoforms are both detected on Western blot, and the ratio of isoforms is the same in both genotypes. Although the level of PR is reduced in the ERKO uterus, the receptor level is sufficient to induce genomic responses, since both calcitonin and amphiregulin mRNAs were increased after progesterone treatment. Finally, the ERKO uterus can be induced to undergo a progesterone-dependent decidual response. Surprisingly, the decidual response is estrogen independent in the ERKO, although it remains estrogen dependent in a wild type. These results indicate that estrogen receptor [Alpha] modulation of PR levels is not necessary for expression of the PR or genomic and physiologic responses to progesterone in the ERKO uterus.

Steroid receptor coactivator-1 (SRC-1) family members interact with steroid receptors, including estrogen receptor [Alpha] (ER[Alpha]) and progesterone receptor (PR), to enhance ligand-dependent transcription. However, the expression of ER[Alpha] and SRC-1 was found to be segregated in distinct subsets of cells within the epithelium of the estrogen-responsive rat mammary gland. This finding was in contrast to the finding for the stroma, where significant numbers of cells coexpressed ER[Alpha] and SRC-1. Treatment of animals with estrogen induced PR expression in the ER[Alpha]-expressing mammary epithelial cells in the absence of detectable SRC-1 and did not affect the segregated pattern of SRC-1 and ER[Alpha] expression. PR was neither expressed nor induced by estrogen treatment in stroma, despite the coexpression of ER[Alpha] and SRC-1. These results suggest that SRC-1 is not necessary for ER[Alpha]-mediated induction of PR in mammary epithelial cells and is also not sufficient for PR induction in stromal cells expressing both ER[Alpha] and SRC-1. Furthermore, the expression of SRC-1 in a subpopulation of mammary epithelial cells distinct from those expressing ER[Alpha] or PR raises the possibility that SRC-1 has cell type-specific functions other than simply to act as coactivator for ER[Alpha] or PR in the mammary epithelium.

Research has established the atomic structure of a progesterone-bound ligand-binding domain existing in the human progesterone receptor. The 1.8 angstrom crystal structure is illustrated. Dimerization studies show that the progesterone receptor varies from other receptors in the group. Structural evidence suggests that 3-keto-steroid receptors may have similar functional characteristics to the progesterone receptor.

The 2.8-[Angstrom] crystal structure of the complex formed by estradiol and the human estrogen receptor-[Alpha] ligand binding domain (hER[Alpha]LBD) is described and compared with the recently reported structure of the progesterone complex of the human progesterone receptor ligand binding domain, as well as with similar structures of steroid/nuclear receptor LBDs solved elsewhere. The hormone-bound hER[Alpha]LBD forms a distinctly different and probably more physiologically important dimer interface than its progesterone counterpart. A comparison of the specificity determinants of hormone binding reveals a common structural theme of mutually supported van der Waals and hydrogen-bonded interactions involving highly conserved residues. The previously suggested mechanism by which the estrogen receptor distinguishes estradiol's unique 3-hydroxy group from the 3-keto function of most other steroids is now described in atomic detail. Mapping of mutagenesis results points to a coactivator-binding surface that includes the region around the 'signature sequence' as well as helix 12, where the ligand-dependent conformation of the activation function 2 core is similar in all previously solved steroid/nuclear receptor LBDs. A peculiar crystal packing event displaces helix 12 in the hER[Alpha]LBD reported here, suggesting a higher degree of dynamic variability than expected for this critical substructure.

Recently generated progesterone receptor (PR)-negative ([PR.sup.-/-]) mice provide an excellent model for dissecting the role of progesterone in the development of the mammary gland during puberty and pregnancy. However, the full extent of the mammary gland defect in these mice caused by the absence of the PR cannot be assessed, because [PR.sup.-/-] mice do not exhibit estrous cycles and fail to become pregnant. To circumvent this difficulty, we have transplanted [PR.sup.-/-] breasts into wild-type mice, and we have demonstrated that the development of the mammary gland in the absence of the PR is arrested at the stage of the simple ductal system found in the young virgin mouse. Mammary transplants lacking the PR in the stromal compartment give rise to normal alveolar growth, whereas transplants containing [PR.sup.-/-] epithelium conserve the abnormal phenotype. Chimeric epithelia in which [PR.sup.-/-] cells are in close vicinity to PR wild-type cells go through complete alveolar development to which the [PR.sup.-/-] cells contribute. Together', these results indicate that progesterone acts by a paracrine mechanism on a subset of mammary epithelial cells to allow for alveolar growth and that expression of the PR is not required in all the cells of the mammary epithelium in order for alveolar development to proceed normally.

Pregnancy maintenance in animals relies on the steroid hormone progesterone (P4), which maintains uterine inactivity by reducing uterine sensitivity to the uterotonic peptide hormone oxytocin. A new study reveals that P4's effect on uterine sensitivity to oxytocin involves a non-genomic action on the uterine oxytocin receptor, which belongs to the G-protein-coupled receptor family. This is the first evidence of a functional interaction between a G-protein linked member and a steroid.