Cloning and sequencing of human LH/hCG receptor cDNA

The effect of controlled ovarian hyperstimulation on ovarian reserve via PTEN pathway

Abstract

This study was carried out to investigate whether repeated controlled ovarian hyperstimulation (COH) affects ovarian reserve. For this reason, we aimed to show possible changes in the expression of PTEN and FOXO3, which are involved in preserving the over-reserve, after applying the COH protocol methods. For this purpose, 18 young Wistar albino female rats (8 weeks old) were randomly assigned as group 1 (control), group 2, and group 3 as 6 subjects in each group. Experimental groups were treated with 10 IU/0.1 mL pregnant mare's serum gonadotropin and a COH protocol consisting of 10 IU/0.1 mL human chorionic gonadotropin injection after 48 h. This procedure was applied three and five times to group 2 and group 3, respectively. For the control groups, the same procedures were performed with 0.1 mL of 0.9% sodium chloride solution. At the end of the experiment, the ovarium tissues were placed in a 10% neutral formaldehyde solution for light microscopic examinations. In histological sections stained with hematoxylin and eosin, the number of ovarian follicles was determined using the physical dissector method. However, the expression of PTEN, FOXO3, and LH-R molecules was evaluated by immunohistochemical methods. As a result of our study, it was concluded that COH administration reduces the expression levels of PTEN and FOXO3 proteins and LH-R, which are among the essential components of the PIK3 intracellular signaling pathway and also increased the levels of hormones such as follicle-stimulating hormone, estradiol, and luteinizing hormone, which are over-reserve markers, and causes adverse effects on the histological structure, oocyte morphology, and number of ovaries.

Lay summary

Today, approximately 10-15% of couples experience fertility problems. However, assisted reproductive techniques help people with fertility problems to get pregnant. The main purpose of these techniques is to put the sperm and egg together outside the woman's body where the eggs are fertilized and then to return the fertilized eggs (embryos) to the womb. During a woman's menstrual cycle, several hormones influence the growth of the eggs. This process can be mimicked by using various medications. Medication is given to increase the number of eggs that develop. However, this method is not the same as normal ovulation. Therefore, in our study, we wanted to examine the effect that developing multiple follicles has on the number and quality of eggs remaining for the future.

The Cell Type-Specific Expression of Lhcgr in Mouse Ovarian Cells: Evidence for a DNA-Demethylation-Dependent Mechanism

The luteinizing hormone receptor (LHCGR) is expressed at low levels in mural granulosa cells and cumulus cells of antral follicles and is induced dramatically in granulosa cells but not in cumulus cells by follicle-stimulating hormone (FSH). Therefore, we hypothesized that FSH not only activates transcription factors controlling Lhcgr expression but also alters other events to permit and enhance Lhcgr expression in granulosa cells but not in cumulus cells. In granulosa cells, the level of DNA methylation in the Lhcgr promoter region was significantly decreased by equine chorionic gonadotropin (eCG) in vivo. However, in cumulus cells, hypermethylation of the Lhcgr promoter remained after eCG stimulation. eCG induced estrogen production from testosterone (T) and retinoic acid (RA) synthesis in granulosa cells. When either T or RA in the presence or absence of FSH was added to granulosa cell cultures, the combined treatment with FSH and RA induced demethylation of Lhcgr-promoter region and Lhcgr expression. FSH-dependent RA synthesis was negatively regulated by coculture of granulosa cells with denuded oocytes, suggesting that oocyte-secreted factors downregulate RA production in cumulus cells where Lhcgr expression was not induced. Strikingly, treatment of cultured cumulus-oocyte complexes with a SMAD inhibitor, SB431542, significantly induced RA production, demethylation of Lhcgr-promoter region, and Lhcgr expression in cumulus cells. These results indicate the demethylation of the Lhcgr-promoter region is mediated, at least in part, by RA synthesis and is a key mechanism regulating the cell type-specific differentiation during follicular development.

The polymorphic insertion of the luteinizing hormone receptor "insLQ" show a negative association to LHR gene expression and to the follicular fluid hormonal profile in human small antral follicles

The luteinizing hormone receptor (LHCGR) has a little studied polymorphic 6 bp insertion (rs4539842/insLQ). This study has evaluated the insLQ polymorphism in relation to potential associations with hormonal characteristics of human small antral follicles (hSAFs). In total, 310 hSAFs were collected from 86 women undergoing fertility preservation. Analysis included hormonal profile of 297 follicular fluid (FF) samples and 148 corresponding granulosa cells samples were evaluated by qPCR for selected genes. Significantly reduced and non-detectable mRNA levels of anti-Müllerian hormone receptor II (AMHR2) and LHCGR, respectively, were observed for insLQ/insLQ compared to -/insLQ and the -/- genotypes. Moreover, LHCGR and CYP19a1 together with oestradiol and inhibin-B were significantly increased in -/insLQ compared to the -/- genotype. The homozygous insLQ genotype showed strong significant associations to GC specific genes LHCGR and CYP19a1, which may translate into significant changes in FF hormone profiles and an altered LH signaling.

Expression of the gonadotropin receptors during follicular development

Background

Gonadotropins induce follicular development that leads to ovulation and luteinization. In women, the level of gonadotropins, along with the expression of their receptors, changes dynamically throughout the menstrual cycle. This study aimed to clarify the mechanisms underlying these phenomena.

Methods

The literature was reviewed, including that published by the authors.

Main findings (Results)

Follicle‐stimulating hormone receptor expression in the granulosa cells was induced by androgens that were derived from growth differentiation factor‐9‐stimulated theca cells. In the theca cells, luteinizing hormone receptor (LHR) expression was noted from their appearance. In the granulosa cells, follicle‐stimulating hormone (FSH) stimulation was essential for LHR expression. However, FSH alone was not sufficient to respond to the luteinizing hormone (LH) surge for oocyte maturation, ovulation, and subsequent luteinization. To achieve these stages, various local factors that were derived from the granulosa and theca cells in response to FSH and LH stimulation had to work synergistically in an autocrine/paracrine manner to strongly induce LHR expression. Following the LH surge, the LHR expression decreased markedly; miRNAs were involved in this transient LHR downregulation. Following ovulation, LHR expression drastically increased again toward luteinization.

Conclusion

The expression of gonadotropin receptors is controlled by sophisticated and complicated systems; a breakdown of this system could lead to ovulation disorders.

Demonstration of the Coexistence of Duplicated LH Receptors in Teleosts, and Their Origin in Ancestral Actinopterygians

Pituitary gonadotropins, FSH and LH, control gonad activity in vertebrates, via binding to their respective receptors, FSHR and LHR, members of GPCR superfamily. Until recently, it was accepted that gnathostomes possess a single FSHR and a single LHR, encoded by fshr and lhcgr genes. We reinvestigated this question, focusing on vertebrate species of key-phylogenetical positions. Genome analyses supported the presence of a single fshr and a single lhcgr in chondrichthyans, and in sarcopterygians including mammals, birds, amphibians and coelacanth. In contrast, we identified a single fshr but two lhgcr in basal teleosts, the eels. We further showed the coexistence of duplicated lhgcr in other actinopterygians, including a non-teleost, the gar, and other teleosts, e.g. Mexican tetra, platyfish, or tilapia. Phylogeny and synteny analyses supported the existence in actinopterygians of two lhgcr paralogs (lhgcr1/ lhgcr2), which do not result from the teleost-specific whole-genome duplication (3R), but likely from a local gene duplication that occurred early in the actinopterygian lineage. Due to gene losses, there was no impact of 3R on the number of gonadotropin receptors in extant teleosts. Additional gene losses during teleost radiation, led to a single lhgcr (lhgcr1 or lhgcr2) in some species, e.g. medaka and zebrafish. Sequence comparison highlighted divergences in the extracellular and intracellular domains of the duplicated lhgcr, suggesting differential properties such as ligand binding and activation mechanisms. Comparison of tissue distribution in the European eel, revealed that fshr and both lhgcr transcripts are expressed in the ovary and testis, but are differentially expressed in non-gonadal tissues such as brain or eye. Differences in structure-activity relationships and tissue expression may have contributed as selective drives in the conservation of the duplicated lhgcr. This study revises the evolutionary scenario and nomenclature of gonadotropin receptors, and opens new research avenues on the roles of duplicated LHR in actinopterygians.

The Role of Human Chorionic Gonadotropin as Tumor Marker: Biochemical and Clinical Aspects

Tumor markers are biological substances that are produced/released mainly by malignant tumor cells, enter the circulation in detectable amounts and are potential indicators of the presence of a tumor. The most useful biochemical markers are the tumor-specific molecules, i.e., receptors, enzymes, hormones, growth factors or biological response modifiers that are specifically produced by tumor cells and not, or minimally, by the normal counterpart (Richard et al. Principles and practice of gynecologic oncology. Wolters Kluwer Health, Philadelphia, 2009). Based on their specificity and sensitivity in each malignancy, biomarkers are used for screening, diagnosis, disease monitoring and therapeutic response assessment in clinical management of cancer patients.This chapter is focused on human chorionic gonadotropin (hCG), a hormone with a variety of functions and widely used as a tumor biomarker in selected tumors. Indeed, hCG is expressed by both trophoblastic and non-trophoblastic human malignancies and plays a role in cell transformation, angiogenesis, metastatization, and immune escape, all process central to cancer progression. Of note, hCG testing is crucial for the clinical management of placental trophoblastic malignancies and germ cell tumors of the testis and the ovary. Furthermore, the production of hCG by tumor cells is accompanied by varying degrees of release of the free subunits into the circulation, and this is relevant for the management of cancer patients (Triozzi PL, Stevens VC, Oncol Rep 6(1):7-17, 1999).The name chorionic gonadotropin was conceived: chorion derives from the latin chordate meaning afterbirth, gonadotropin indicates that the hormone is a gonadotropic molecule, acting on the ovaries and promoting steroid production (Cole LA, Int J Endocrinol Metab 9(2):335-352, 2011). The function, the mechanism of action and the interaction between hCG and its receptor continue to be the subject of intensive investigation, even though many issues about hCG have been well documented (Tegoni M et al., J Mol Biol 289(5):1375-1385, 1999).

Association between the luteinizing hormone/chorionic gonadotropin receptor (LHCGR) rs4073366 polymorphism and ovarian hyperstimulation syndrome during controlled ovarian hyperstimulation

BACKGROUND

The aim of this study was to determine the relationship between a purported luteinizing hormone/chorionic gonadotropin (LHCGR) high function polymorphism (rs4539842/insLQ) and outcome to controlled ovarian hyperstimulation (COH).

METHODS

This was a prospective study of 172 patients undergoing COH at the Fertility and IVF Center at GWU. DNA was isolated from blood samples and a region encompassing the insLQ polymorphism was sequenced. We also investigated a polymorphism (rs4073366 G > C) that was 142 bp from insLQ. The association of the insLQ and rs4073366 alleles and outcome to COH (number of mature follicles, estradiol level on day of human chorionic gonadotropin (hCG) administration, the number of eggs retrieved and ovarian hyperstimulation syndrome (OHSS)) was determined.

RESULTS

Increasing age and higher day 3 (basal) FSH levels were significantly associated with poorer response to COH. We found that both insLQ and rs4073366 were in linkage disequilibrium (LD) and no patients were homozygous for both recessive alleles (insLQ/insLQ; C/C). The insLQ variant was not significantly associated with any of the main outcomes to COH. Carrier status for the rs4073366 C variant was associated (P = 0.033) with an increased risk (OR 2.95, 95% CI = 1.09-7.96) of developing OHSS.

CONCLUSIONS

While age and day 3 FSH levels were predictive of outcome, we found no association between insLQ and patient response to COH. Interestingly, rs4073366 C variant carrier status was associated with OHSS risk. To the best of our knowledge, this is the first report suggesting that LHCGR genetic variation might function in patient risk for OHSS.

Association of a missense mutation in the luteinizing hormone/choriogonadotropin receptor gene (LHCGR) with superovulation traits in Chinese Holstein heifers

Background

Upon binding luteinizing hormone in the ovary, the luteinizing hormone/choriogonadotropin receptor (LHCGR) is necessary for follicular maturation and ovulation, as well as luteal function. We detected mutations in the LHCGR gene and evaluated their association with superovulation.

Methods

Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing, we examined polymorphisms in LHCGR and the genotypes associated with superovulation traits in 127 Chinese Holstein heifers.

Results

A G/T polymorphism (ss52050737) in exon 11 was significantly associated with the total number of ova and the number of transferable embryos.

Conclusions

LHCGR may be a new predictor for superovulation in Chinese Holstein heifers.

Structure, function and regulation of gonadotropin receptors - a perspective

Luteinizing hormone receptor and follicle stimulating hormone receptor play a crucial role in female and male reproduction. Significant new information has emerged about the structure, mechanism of activation, and regulation of expression of these receptors. Here we provide an overview of the current information on those aspects with an in-depth discussion of the recent developments in the post-transcriptional mechanism of LH receptor expression mediated by a specific LH receptor mRNA binding protein, designated as LRBP. LRBP was identified by electrophoretic gel mobility shift assay using cytosolic fractions from ovaries in the down regulated state. LRBP was purified, its binding site on LH receptor mRNA was identified and characterized. During ligand-induced down regulation, LRBP expression is increased through the cAMP/PKA and ERK signaling pathway, is translocated to translating ribosomes, binds LH receptor mRNA and forms an untranslatable ribonucleoprotein complex. This complex is then routed to the mRNA degradation machinery resulting in diminished levels of both LHR mRNA and cell surface expression of LH receptor. The studies leading to these conclusions are presented.

Participation of signaling pathways in the derepression of luteinizing hormone receptor transcription

The luteinizing hormone receptor (LHR) transcription is subject to an epigenetic regulatory mode whereby the proximal Sp1 site acts as an anchor to recruit histone deacetylases (HDAC)1/2 and the Sin3A co-repressor complex. This results in promoter-localized histone hypo-acetylation that contributes to the silencing of LHR transcriptional expression. Chromatin changes resulting from site-specific acetylation and methylation of histones regulate LHR gene expression. The HDAC inhibitor TSA-induced cell-specific phosphatase release from the promoter, which serves as an 'on' mechanism for Sp1 phosphorylation by phosphatidylinositol 3-kinase/protein kinase Czeta (PI3K/PKCzeta) at Ser641, leading to p107 repressor derecruitment and LHR transcriptional activation. The methylation status of the promoter provides another layer of modulation in a cell-specific manner. Maximal derepression of the LHR gene is dependent on complete DNA demethylation of the promoter in conjunction with histone hyperacetylation and release of repressors (p107 and HDAC/Sin3A). Independently, the PKC-alpha/Erk pathway, participates in LHR gene expression through induction of Sp1 phosphorylation at Ser site(s) other than Ser641. This causes dissociation of the HDAC1/mSin3A from the promoter, recruitment of TFIIB and Pol II, and transcriptional activation. Collectively, these findings demonstrate that LHR gene expression at the transcriptional level is regulated by complex and diverse networks, in which coordination and interactions between these regulatory effectors are crucial for silencing/activation of LHR expression.

Novel C617Y mutation in the 7th transmembrane segment of luteinizing hormone/choriogonadotropin receptor in a Japanese boy with peripheral precocious puberty

Testotoxicosis, also known as familial male-limited precocious puberty, is an autosomal dominant form of gonadotropin-independent precocious puberty caused by heterozygous constitutively activating mutations of the LHCGR gene encoding the luteinizing hormone/choriogonadotropin receptor (LH/CGR). The patient is an 8-year-old boy who started to develop pubic hair and penile enlargement at 6 years of age. The patient had elevated serum testosterone levels, but initially exhibited a prepubertal response of gonadotropins to GnRH, which was followed by central activation of the hypothalamo-pituitary-gonadal axis. The father reported having experienced precocious puberty, and is 158 cm tall. There is no history of short stature and precocious puberty in the family except for the father. The LHCGR gene was analyzed by direct DNA sequencing of amplified PCR products from the patient and his parents. The wild-type and mutant LH/CGRs were transiently expressed in COS-1 cells and cAMP levels in the cells were determined with or without hCG stimulation. Genetic analysis revealed a novel C617Y mutation of the LHCGR gene in the patient and his mother, while his father had no mutations. Functional expression study demonstrated around 15% increase in the basal intracellular cAMP level in cells expressing the mutant LH/CGR compared with that in cells expressing the wild-type receptor. We have reported the first missense C617Y mutation located in the 7th transmembrane segment of LH/CGR causing testotoxicosis. The modest phenotype of our patient may be explained, at least in part, by the modest increase in the intracellular cAMP level caused by the C617Y mutation.

G protein-coupled receptors of the hypothalamic-pituitary-gonadal axis: a case for Gnrh, LH, FSH, and GPR54 receptor ligands

The hypothalamic-pituitary-gonadal (HPG) axis, important in reproduction and sex hormone-dependent diseases, is regulated by a number of G protein-coupled receptors. The recently "deorphanized" GPR54 receptor activated by the peptide metastin is thought to be the key regulator of the axis, mainly by releasing gonadotropin-releasing hormone (GnRH) from the hypothalamus. The latter decapeptide, through the activation of the GnRH receptor in the anterior pituitary, causes the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which subsequently activate their respective receptors on the gonadotrope cells. In this review we will discuss the small molecule agonists and antagonists that are currently being developed to intervene with the action of these four receptors. For GnRH receptors, 14 different chemical classes of non-peptidic antagonists have been reported, while for the LH receptor three classes of agonists have been described. Both agonists and antagonists have been introduced for the FSH receptor. Recently, the first non-peptidic agonist for GPR54 was reported.

The cloned equine thyrotropin receptor is hypersensitive to human chorionic gonadotropin; identification of three residues in the extracellular domain involved in ligand specificity

The receptors for TSH, LH/chorionic gonadotropin (CG), and FSH belong to the same subfamily of G protein-coupled receptors. The specificity of recognition of their cognate hormone involves a limited number of residues in the leucine-rich repeats present in the N-terminal ectodomain of the receptor. It is admitted that receptors of this subfamily coevoluted with their respective ligands. The secretion of CG is restricted to gestation of primates and Equidae. We hypothesized that, facing the challenge of a new hormone, the glycoprotein hormone receptors would have evolved differently in Equidae and human so that distinct residues are involved in hormone specificity. In particular, it is known that equine CG has a dual (FSH and LH) activity when administered to other species. In the present work, we cloned and characterized functionally the equine TSH receptor (TSHR), which shares 89% homology with the human TSHR. The equine TSHR is not responsive to equine CG but is more sensitive to human CG than the human TSHR. Three residues, at positions 60, 229, and 235 of the ectodomain, are responsible for this difference in sensitivity as shown by modelization and targeted mutagenesis, followed by in vitro functional characterization. The phylogenetic approach is a suitable approach to identify determinants of specificity of receptors.

Human chorionic villous macrophages as a fetal biological shield from maternal chorionic gonadotropin

In addition to its most well characterized biological role in the rescue and maintenance of corpus luteum function, human chorionic gonadotropin (hCG) also stimulates the onset of fetal gonadal steroidogenesis. However, excess hCG is teratogenic to fetal gonadal tissues, and therefore hCG must be tightly regulated. Although there is an anatomical barrier between the fetal vessels and maternal blood, other mechanisms may regulate hCG levels. In the present study, we investigated whether human chorionic villous macrophages degraded maternal hCG. Isolated human macrophages incorporated and degraded hCG in a time-dependent manner. Human placental villous macrophages and phorbol myristate acetate (PMA)-treated THP-1 cells expressed the gene encoding an exon 9-deleted form of the luteinizing hormone/chorionic gonadotropin (LH/CG) receptor; expression of the full-length receptor was not determined. While both PMA-treated or untreated THP-1 cells could uptake hCG into their cytoplasms, hCG degradation and excretion of its byproducts only progressed in PMA-treated THP-1 cells. In conclusion, hCG internalization and degradation are different processes in macrophages that protect fetal gonadogenesis from excess hCG. The exon 9-deleted LH/CG receptor, but not the full-length receptor, is involved in the degradation of cytoplasmic hCG by organ-specific, dominant-negative interactions.

Effect of estrogen on the expression of luteinizing hormone-human chorionic gonadotropin receptor messenger ribonucleic acid in cultured rat granulosa cells

Estrogen has been considered to enhance FSH actions in the ovary, including the induction of the LH receptor (LHR). In this study, we elucidated the mechanism underlying the effect of estrogen on the induction of LHR by FSH in rat granulosa cells. Estradiol clearly enhanced the FSH-induced LHR mRNA increase in a time- and dose-dependent manner, with a maximum increase of approximately 3.5-fold at 72 h, compared with the level of LHR mRNA solely induced by FSH. We then investigated whether the effect of estrogen on LHR mRNA was due to increased transcription and/or altered mRNA stability. A luciferase assay with the plasmid containing the LHR 5'-flanking region did not show that estradiol increased the promoter activity induced by FSH. In contrast, the decay curves for LHR mRNA showed a significant increase in half-life with FSH and estradiol, suggesting that the increased stability of LHR mRNA is at least responsible for the regulation of LHR mRNA by estrogen. Recently mevalonate kinase (Mvk) was identified as a trans-factor that binds to LHR mRNA and alters LHR mRNA stability in the ovary. We found that estradiol, with FSH, decreased Mvk mRNA levels in rat granulosa cell culture, resulting in up-regulation of LHR mRNA that was inversely correlated to Mvk mRNA expression. Furthermore, the augmentation of FSH-induced LHR expression in the presence of estrogen was erased with the overexpression of Mvk by transient transfection. Taken together, these data indicate that LHR mRNA is up-regulated due to increased stability when estrogen negatively controls Mvk.

Regulation of human luteinizing hormone receptor in the ovary

The luteinizing hormone receptor (LHR) is essential for elevated levels of progesterone to maintain pregnancy during the first trimester; the maintenance of the expression of LHR is a key factor controlling the duration of luteal function. Therefore, as the expression of LHR is most likely to be regulated by the stability of the receptor mRNA at the luteal phase of the human menstrual cycle, we focused on studies examining the stability of mRNA rather than the production of mRNA. In addition, LHR (exon 9), one of the splice variants of human LHR (hLHR), was cloned in the corpus luteum of a patient with a regular menstrual cycle. The results of Western blots using Percoll gradient fractionation indicated that hLHR formed complexes with hLHR (exon 9), which are transferred to the lysosome, where they are eventually degraded, instead of being translocated from the endoplasmic reticulum to the transducing organelle. These results showed that hLHR (exon 9) caused a reduction in the expression of functional receptor number and affected the signaling condition of wild-type hLHR. As the luteal phase progressed hLHR (exon 9) increased relative to hLHR, demonstrating that hLHR (exon 9) was expressed more than hLHR in the late luteal phase. This work reveals the essential function of the regulatory and structural elements involved in human LH receptor splicing, and that hLHR (exon 9) can negatively control the function of wild-type receptors. Moreover, this finding presented a novel mechanism of regulation of LHR in the human corpus luteum. (Reprod Med Biol 2008; 7: 11-16).

Human placental development is impaired by abnormal human chorionic gonadotropin signaling in trisomy 21 pregnancies

Placental development is markedly abnormal in women bearing a fetus with trisomy 21, with defective syncytiotrophoblast (ST) formation and function. The ST occurs from cytotrophoblast (CT) fusion and plays an essential role by secreting human chorionic gonadotropin (hCG), which is essential to placental development. In trisomy of chromosome 21 (T21) pregnancies, CTs do not fuse and differentiate properly into STs, leading to the secretion of an abnormal and weakly bioactive hCG. In this study we report for the first time, a marked decrease in the number of mature hCG receptor (LH/CG-R) molecules expressed at the surface of T21-affected CTs. The LH/CG-R seems to be functional based on sequencing that revealed no mutations or deletions and binding of recombinant hCG as well as endogenous hCG. We hypothesize that weakly bioactive hCG and lower LH/CG-R expression may be involved in the defect of ST formation. Interestingly, the defective ST formation is mimicked in normal CT cultures by using LH/CG-R small interfering RNA, which result in a lower hCG secretion. Furthermore, treatment of T21-affected CTs with recombinant hCG overcomes in vitro the T21 phenotype, allowing CTs to fuse and form a large ST. These results illustrate for the first time in trisomy 21 pathology, how abnormal endogenous hCG signaling impairs human placental development.

TSH receptor antibodies

The discovery of thyroid-stimulating autoantibodies by Adams and Purves 50 years ago was one of the most important observations in the history of thyroidology. Since that time, the thyroid-stimulating hormone receptor (TSHR) has been shown to be the antigen recognized by these autoantibodies (1974) and the receptor cloned (1989). More recently, different mouse monoclonal antibodies (MAbs) to the TSHR have been produced, culminating in 2002 in the preparation of mouse and hamster MAbs with strong thyroid-stimulating activity. Further, in 2003 a human MAb to the TSHR (M22) with the characteristics of patient thyroid-stimulating autoantibodies was described. M22 has been particularly useful in advancing our knowledge of the TSHR and TSHR autoimmunity, including the development of new assays for TSHR autoantibodies (2004) and determination of a high-resolution (2.55 A) crystal structure of the TSHR leucine-rich domain in combination with M22 (2007). The structure shows that M22 positions itself on the TSHR in an almost identical way to the native hormone TSH but the evolutionary forces that have resulted in production of a common autoantibody that mimics the actions of TSH so well are far from clear at this time. Very recently, a human MAb (5C9) with the characteristics of blocking-type patient serum TSHR autoantibodies has been isolated (2007). Studies on how 5C9 interacts with the TSHR at the molecular level are planned and should provide key insights as to the differences between TSHR autoantibodies with blocking and with stimulating activities. Also, 5C9 and similar MAbs have considerable potential as drugs to inhibit TSHR stimulation by autoantibodies. Further, now the M22-TSHR structure is known at the atomic level, rational design of specific low-molecular-weight inhibitors of the TSHR-TSHR autoantibody interaction is feasible.

Biochemical characterization and modulation of LH/CG-receptor during human trophoblast differentiation

Due to the key role of the human chorionic gonadotropin hormone (hCG) in placental development, the aim of this study was to characterize the human trophoblastic luteinizing hormone/chorionic gonadotropin receptor (LH/CG-R) and to investigate its expression using the in vitro model of human cytotrophoblast differentiation into syncytiotrophoblast. We confirmed by in situ immunochemistry and in cultured cells, that LH/CG-R is expressed in both villous cytotrophoblasts and syncytiotrophoblasts. However, LH/CG-R expression decreased during trophoblast fusion and differentiation, while the expression of hCG and hPL (specific markers of syncytiotrophoblast formation) increased. A decrease in LH/CG-R mRNA during trophoblast differentiation was observed by means of semi-quantitative RT-PCR with two sets of primers. A corresponding decrease ( approximately 60%) in LH/CG-R protein content was shown by Western-blot and immunoprecipitation experiments. The amount of the mature form of LH/CG-R, detected as a 90-kDa band specifically binding (125)I-hCG, was lower in syncytiotrophoblasts than in cytotrophoblasts. This was confirmed by Scatchard analysis of binding data on cultured cells. Maximum binding at the cell surface decreased from 3,511 to about 929 molecules/seeded cells with a kDa of 0.4-0.5 nM. Moreover, on stimulation by recombinant hCG, the syncytiotrophoblast produced less cyclic AMP than cytotrophoblasts, indicating that LH/CG-R expression is regulated during human villous trophoblast differentiation.

Localization and variable expression of G alpha(i2) in human endometrium and Fallopian tubes

BACKGROUND

Heterotrimeric G proteins take part in membrane-mediated cell signalling and have a role in hormonal regulation. This study clarifies the expression and localization of the G protein subunit G alpha(i2) in the human endometrium and Fallopian tube and changes in G alpha(i2) expression in human endometrium during the menstrual cycle.

METHODS

The expression of G alpha(i2) was identified by Polymerase chain reaction (PCR), and localization confirmed by immunostaining. Cyclic changes in G alpha(i2) expression during the menstrual cycle were evaluated by quantitative real-time PCR.

RESULTS

We found G alpha(i2) to be expressed in human endometrium, Fallopian tube tissue and in primary cultures of Fallopian tube epithelial cells. Our studies revealed enriched localization of G alpha(i2) in Fallopian tube cilia and in endometrial glands. We showed that G alpha(i2) expression in human endometrium changes significantly during the menstrual cycle, with a higher level in the secretory versus proliferative and menstrual phases (P < 0.05).

CONCLUSIONS

G alpha(i2) is specifically localized in human Fallopian tube epithelial cells, particularly in the cilia, and is likely to have a cilia-specific role in reproduction. Significantly variable expression of G alpha(i2) during the menstrual cycle suggests G alpha(i2) might be under hormonal regulation in the female reproductive tract in vivo.

The effect of splice variant of the human luteinizing hormone (LH) receptor on the expression of gonadotropin receptor

A splice variant of human lutropin/choriogonadotropin-receptor [hLHR (exon 9)] that lacks exon 9 was previously cloned in the corpus luteum of a woman with a regular menstrual-cycle. Supported by detergent soluble binding assay and receptor biotinylation experiment, the receptor binding assay shows hLHR (exon 9) is neither expressed at the cell surface nor have the capability of binding to hCG. Interactions between hLHR (exon 9) with the immature bands of gonadotropin receptors not with the mature bands were seen. This phenomenon is specific among gonadotropin receptors since human thyrotropin-receptor (hTSHR) failed to be coimmunoprecipitated. Furthermore, this receptor complex attenuated the receptor protein level within the cells. To elucidate the mechanism underlying the decrease in receptor protein by this receptor complex, we performed a Percoll-fractionation experiment, which indicated the receptor complex drove hLHR to the lysosome instead of the plasma-membrane. Moreover, the expression of hLHR (exon 9) mRNA was seen at all phases of the menstrual cycle and relatively increased as the luteal phase progressed. These results reveal a novel mechanism of regulation for gonadotropin receptor expression.

Radiation exposure impairs luteinizing hormone signal transduction and steroidogenesis in cultured human leydig cells

Therapeutic, accidental, and experimental radiation exposures decreased serum testosterone in males, leading to various sexual problems. Since testicular Leydig cells are the predominant source of circulating testosterone, findings on the direct effects of radiation on Leydig cell steroidogenesis and the mechanism behind such effects would be of greater importance to the use of safer radiation doses in cancer therapy and to adopt preventive or therapeutic measures to alleviate postirradiation lesions, respectively. Therefore, this study was undertaken to explore the same using cultured human Leydig cells. Testicles removed from advanced prostatic carcinoma patients were used for isolation and purification of Leydig cells. Purified Leydig cells were cultured and then exposed to different doses (2, 4, 6, 8, and 10 Gy) of fractioned gamma radiation. Normal and irradiated cells were used for luteinizing hormone (LH) receptor quantification or total RNA isolation to study LH receptor mRNA expression or LH/cyclic AMP (cAMP) stimulation test. While LH-stimulated cells were used for cAMP assay, LH- and cAMP-stimulated cells were used for the estimation of steroidogenic enzymes, testosterone and estradiol production. Radiation exposure caused adverse effects on Leydig cell steroidogenesis in a dose-dependent manner. While lower doses (2 and 4 Gy) were ineffective, higher doses (6 Gy and above) drastically decreased LH receptor, basal and LH-stimulated cAMP generation, and basal, LH-, and cAMP-stimulated steroidogenesis. While 2 Gy of radiation exposure increased the LH receptor mRNA level, other doses did not induce any significant change. Therefore, it is concluded that higher doses of radiation impair Leydig cell steroidogenesis by affecting LH signal transduction at the level of both pre- and post-cAMP generation. Decreased level of LH receptors following higher doses of radiation exposure is not coupled with impaired expression of its mRNA.

[Leydig cell hypoplasia]

The Leydig cell hypoplasia is a rare and well defined form of male pseudohermaphroditism with autosomal recessive inheritance pattern. An inadequate fetal testicular Leydig cell differentiation and, consequently a low androgenic production during intra uterine and post natal periods, result in absence or incomplete virilization in patients with 46,XY karyotype. These patients exhibit a wide clinical spectrum, ranging from complete female external genitalia to male external genital with micropenis, low serum testosterone levels associated with high LH levels. Inactivating mutations of the LH/hCG receptor gene have been identified in affected families in the last decade. However, the low frequency of inactivating mutations in this gene, and the lack of segregation of intragenic polymorphisms among affected members from families with typical phenotype of Leydig cell hypoplasia, suggest the genetic heterogeneity of this condition.

Follicle-stimulating hormone receptor gene mutations are not evident in Greek women with premature ovarian failure and poor responders

BACKGROUND/AIMS

This clinical and molecular study aimed to investigate the presence of follicle-stimulating hormone (FSH) receptor gene mutations in women with premature ovarian failure (POF) and poor responders to in vitro fertilization treatment.

METHODS

DNA was extracted from blood samples for subsequent polymerase chain reaction (PCR). PCR was followed by restriction fragment length polymorphism and direct sequencing.

RESULTS

No inactivating mutations reported so far were identified in exons 6, 7, and 10 in women with POF and poor responders.

CONCLUSION

FSH receptor gene mutations are not frequent in Greek patients with POF as is the case in the rest of the world except for cases with ovarian dysgenesis in Finland.

Differential inhibition of Scutellaria barbata D. Don (Lamiaceae) on HCG-promoted proliferation of cultured uterine leiomyomal and myometrial smooth muscle cells

Scutellaria barbata D. Don (Lamiaceae)(SB) is a perennial herb which is natively distributed throughout Korea and southern China. This herb is known in traditional Chinese Medicine as Ban-Zhi-Lian and traditional Korean medicine as Banjiryun, respectively. SB has been used as an anti-inflammatory and antitumor agent. We aimed to determine the expressin of cell cycle-related signal molecules for growth inhibition after HCG treatment by the herb SB in two different human myometrial smooth muscle cells (SMCs) and leiomyomal SMCs. Water-soluble ingredients of SB, myometrial SMCs and the leiomyomal cell lines were used in vitro. Uterine myomas often enlarge rapidly during pregnancy, implying that human chorionic gonadotrophin (HCG) may influences cell proliferation in uterine leiomyomata. We investigated the effects of SB on the cell proliferation and the expression of cell cycle-related proteins in these cells. Although HCG/LH receptor was present in both cultured myometrial and leiomyomal cells, as assayed by reverse transcription polymerase chain reaction analysis, treatment with HCG significantly increased cell proliferation in both myometrial and leiomyomal cells. However, SB reduced the proliferative effect of HCG in leiomyoma and myometrial cells, respectively. In HCG-treated leiomyomal cells, the expression of proliferating cell nuclear antigen, cyclin E and cdc2 was significantly reduced by SB treatment. These results suggest that SB reduced the HCG-promoted proliferation of myometrial and leiomyomal cells.

Fish FSH receptors bind LH: how to make the human FSH receptor to be more fishy?

In mammals, the interactions between glycoprotein hormones and their cognate receptors are highly specific; unintended cross-reactivity under normal physiological conditions has not been observed. The interactions between fish gonadotropins and their receptors, on the other hand, appeared to be less discriminatory. For example, the catfish follicle-stimulating hormone (FSH) receptor was highly responsive to both catfish luteinizing hormone (LH) and catfish FSH. Similarly, the FSH receptor of coho salmon bound both salmon FSH and LH. In contrast, LH receptors of both species were found to be rather specific for their cognate LH. This paper intends to summarize the current situation with special emphasis to our comparative structure-function studies that aim at elucidating the molecular basis of ligand selectivity (in mammals) and ligand promiscuity (in fish).

Association of human follitropin (FSH) receptor with splicing variant of human lutropin/choriogonadotropin receptor negatively controls the expression of human FSH receptor

A splice variant of human lutropin (LH)/choriogonadotropin (CG)-receptor [hLHR(exon 9)] that lacks exon 9 was previously cloned in the corpus luteum of a woman with a normal menstrual cycle. Supported by a detergent-soluble binding assay and a receptor biotinylation experiment, the receptor binding assay shows hLHR(exon 9) is neither expressed at the cell surface nor has the capability of binding to hCG. In addition, hLHR(exon 9) was confirmed in the endoplasmic reticulum (ER) by endoglycosidase H treatment. A coimmunoprecipitation experiment clearly showed that hLHR(exon 9) and constitutively inactivate mutant-LHRs, which stay in the ER, form an association with the human follitropin (FSH)-receptor (hFSHR). This suggests that in the presence of mutant-LHR, hFSHR, which is trapped in the ER and associated with hLHR(exon 9), is unable to come up to the plasma membrane. This phenomenon is specific among gonadotropin receptors because human TSH receptor failed to be coimmunoprecipitated. Furthermore, this receptor complex attenuated the hFSHR receptor protein level within the cells, which impaired cAMP production. To elucidate the mechanism underlying the decrease in hFSHR protein by this receptor complex, we performed a Percoll fractionation experiment, which indicated that the receptor complex drove hFSHR to the lysosome instead of the plasma membrane. These results reveal a novel mechanism of FSHR expression regulation.

Gonadotropin receptors: role of post-translational modifications and post-transcriptional regulation

This review focuses on the post-translational modifications of LH and FSH receptors and recent studies on the regulation of LH receptor expression mediated by an RNA binding protein. Both LH and FSH receptors undergo extensive post-translational modifications. N-linked glycosylation occurs co-translationally and plays a role in the maturation and processing of the receptor, while palmitoylation is involved in receptor endocytosis and post-endocytic trafficking. A third type of post-translational modification is phosphorylation and its function has been reviewed. Finally, the regulation of LH receptor at the mRNA level by an RNA binding protein is discussed in the context of ovarian function.

Expression of the full-length and alternatively spliced equine luteinizing hormone/chorionic gonadotropin receptor mRNAs in the primary corpus luteum and fetal gonads during pregnancy

The full-length equine luteinizing hormone/chorionic gonadotropin (LH/CG) receptor (eLH/CG-RA) cDNA and two alternatively spliced isoforms (eLH/CG-RB,C) were isolated from luteal tissue and characterized using a combination of reverse transcription-polymerase chain reaction (RT-PCR) and 5'-rapid amplification of cDNA ends. The 680-amino acid full sequence of eLH/CG-RA displayed 87-92% homology with other mammalian LH/CG-Rs. The eLH/CG-RB and eLH/CG-RC cDNA isoforms were truncated from the 3'-end of exon X: eLH/CG-RB spliced out of frame into the last exon whereas eLH/CG-RC contained an in-frame stop codon within a divergent sequence. Consequently, both eLH/CG-RB and eLH/CG-RC cDNA isoforms encoded putative proteins without transmembrane and intracellular domains. In order to study the responsiveness of the primary corpus luteum (CL) and fetal gonads to eCG, the expression of eLH/CG-R mRNAs was examined by RT-PCR and Northern blot analysis during early and mid-pregnancy. All three eLH/CG-R cDNA isoforms (eLH/CG-RA,B,C) were expressed from day 14 to day 83 of pregnancy in the primary CL and from day 44 to day 222 in fetal gonads. Interestingly, the primary CL at days 89 and 151 expressed only truncated eLH/CG-R cDNA isoforms. The relative values of Northern hybridized major 7, 5.7, 3.9 and 1.8 kb eLH/CG-R mRNA transcripts tended to decrease in the primary CL whereas the unique major 1.8 kb eLH/CG-R mRNA was steadily expressed in fetal gonads during pregnancy. These results show that the expression of eLH/CG-R mRNAs occurs in the fetal gonads before ceasing in the primary CL and suggest that eCG may be involved in the gradual transition from a luteal to a feto-placental output of steroids during equine pregnancy.

Regulation of luteinizing hormone/human chorionic gonadotropin receptor expression: a perspective

The LH/hCG receptor, a member of the G protein coupled receptor family mediates the cellular actions of LH in the ovary. A considerable amount of information regarding its structure, mechanism of activation, and regulation of expression has emerged in recent years. Here we provide a brief overview of the current information on the structural organization of the receptor and the mechanism of receptor mediated signaling as well as an in-depth discussion on recent developments pertaining to the regulation of receptor expression. Specifically, we describe studies from our laboratory showing that the posttranscriptional regulation of the receptor involves an LH/hCG receptor mRNA-binding protein. We also propose a model to explain the loss of steady-state LH/hCG receptor mRNA levels during receptor down-regulation.

Luteinizing hormone, a reproductive regulator that modulates the processing of amyloid-beta precursor protein and amyloid-beta deposition

Hormonal changes associated with the dysregulation of the hypothalamic-pituitary-gonadal (HPG) axis following menopause/andropause have been implicated in the pathogenesis of Alzheimer's disease (AD). Experimental support for this has come from studies demonstrating an increase in amyloid-beta (Abeta) deposition following ovariectomy/castration. Because sex steroids and gonadotropins are both part of the HPG feedback loop, any loss in sex steroids results in a proportionate increase in gonadotropins. To assess whether Abeta generation was due to the loss of serum 17beta-estradiol or to the up-regulation of serum gonadotropins, we treated C57Bl/6J mice with the anti-gonadotropin leuprolide acetate, which suppresses both sex steroids and gonadotropins. Leuprolide acetate treatment resulted in a 3.5-fold (p < 0.0001) and a 1.5-fold (p < 0.024) reduction in total brain Abeta1-42 and Abeta1-40 concentrations, respectively, after 8 weeks of treatment. To further explore the role of gonadotropins in promoting amyloidogenesis, M17 neuroblastoma cells were treated with the gonadotropin luteinizing hormone (LH) at concentrations equivalent to early adulthood (10 mIU/ml) or post-menopause/andropause (30 mIU/ml). LH did not alter amyloid-beta precursor protein (AbetaPP) expression but did alter AbetaPP processing toward the amyloidogenic pathway as evidenced by increased secretion and insolubility of Abeta, decreased alphaAbetaPP secretion, and increased AbetaPP-C99 levels. These results suggest the marked increases in serum LH following menopause/andropause as a physiologically relevant signal that could promote Abeta secretion and deposition in the aging brain. Suppression of the age-related increase in serum gonadotropins using anti-gonadotropin agents may represent a novel therapeutic strategy for AD.

Studies on the Regulation of Expression of Luteinizing Hormone Receptor in the Ovary and the Mechanism of Follicular Cyst Formation in Ruminants

In the series of studies, changes of expression and regulation of luteinizing hormone (LH) receptor in the ovary of domestic ruminants were examined. Furthermore, mechanisms of formation of follicular cysts in domestic ruminants, caused by stress and so on, were endocrinologically elucidated. Results of the studies provide the following conclusions. (1) The quantity of LH receptor in the bovine antral follicles increases rapidly in the latter stage of its development. (2) The quantity of LH receptor and its mRNA in the bovine and caprine corpus luteum increase during their developments. The increase of the receptor in the caprine luteal development is regulated by LH through the receptor mRNA level. (3) At least, three splice variants of LH receptor mRNA exist in the bovine luteal tissue and the variant receptors are expressed at different cellular sites according to its structure. (4) Intracellular consecutive cysteine residues of LH receptor are palmitoylated and thereby inhibit internalization of the receptor. (5) As a mechanism of the bovine follicular cyst caused by stress, it is suggested that increased secretions of progesterone and cortisol from the adrenal gland exert inhibitory effects on the hypothalamus and follicle, respectively, and subsequently LH and FSH surges are blocked, then finally ovulation is suppressed and the follicle becomes cystic.

Expression and binding activity of luteinizing hormone/chorionic gonadotropin receptors in the primary corpus luteum during early pregnancy in the mare

Luteal steroids are necessary to maintain the first 70-90 days of pregnancy in the mare. At 35 days postovulation, the resurgence of the primary corpus luteum (CL) coincides with the secretion of the fetal hormone eCG. In order to study the responsiveness of the primary CL to eCG, we have examined levels of luteal equine LH/CG receptors (eLH/CG-R) mRNAs by Northern blot analysis and measured concentrations of eLH/CG binding sites on luteal membranes using 125I-eLH saturation binding assays at three stages of gestation: before the onset of eCG secretion (Days 14-31), from onset to maximum eCG secretion (Days 38-62), and during decline of eCG secretion (Days 83-101). Multiple transcripts of eLH/CG-R (7, 5.7, 4.9, 3.9, 2.8, 1.8, 0.6 kilobase [kb]) were identified in the primary CL at all stages examined. Three of them (5.7, 2.8, 0.6 kb) coded for truncated eLH/CG-R lacking the transmembrane domain. The relative intensities of the four major transcripts tended to decrease (5.7 and 3.9 kb) or were steadily expressed (7 and 1.8 kb) during pregnancy. The affinity of eLH/CG binding sites did not change during pregnancy whereas the number of eLH/CG binding sites decreased significantly after the onset of eCG secretion. Nevertheless, levels of binding sites were still at 44.6% (Days 38-62) to 24.7% (Days 83-101) of those measured before the onset of eCG secretion. Taken together, the presence of eLH/CG-R mRNAs and of a substantial part of eLH/CG binding sites with high affinity suggest that the primary CL still expresses a high number of eLH/CG-R and remains responsive to eCG during early pregnancy.

GIPC binds to the human lutropin receptor (hLHR) through an unusual PDZ domain binding motif, and it regulates the sorting of the internalized human choriogonadotropin and the density of cell surface hLHR

By using a yeast two-hybrid screen we identified GIPC (GAIP-interacting protein C terminus), a protein with a type I PDZ domain as a novel human lutropin receptor (hLHR) binding partner. Pull-down and immunoprecipitation assays confirmed this interaction and showed that it is dependent on the PDZ domain of GIPC and the C-terminal tetrapeptide of the hLHR. To characterize the functional consequences of the GIPC-hLHR interaction, we used a small interfering RNA against GIPC to generate a clonal cell line that is deficient in GIPC. Studies with this cell line reveal that GIPC is partially responsible for the recycling of the hormone that is internalized by the hLHR and also for maintaining a relatively constant level of hLHR at the cell surface during hormone internalization.

Multiple luteinizing hormone receptor (LHR) protein variants, interspecies reactivity of anti-LHR mAb clone 3B5, subcellular localization of LHR in human placenta, pelvic floor and brain, and possible role for LHR in the development of abnormal pregnancy, pelvic floor disorders and Alzheimer's disease

Distinct luteinizing hormone receptor (LHR) protein variants exist due to the posttranslational modifications. Besides ovaries, LHR immunoreactivity (LHRI) was also found in other tissues, such as the brain, fallopian tube, endometrium, trophoblast and resident tissue macrophages. The 3B5 mouse monoclonal antibody was raised against purified rat LHR. In rat, porcine and human ovaries, the 3B5 identified six distinct LHR bands migrating at approximately 92, 80, 68, 59, 52 and 48 kDa. Characteristic LHRI was detected in rat, human and porcine corpora lutea. During cellular differentiation, subcellular LHR distribution changed from none to granular cytoplasmic, perinuclear, surface, nuclear and no staining. There were also differences in vascular LHR expression--lack of LHRI in ovarian vessels and strong staining of vessels in other tissues investigated. In normal human term placentae, villous LHRI was associated with blood sinusoids and cytotrophoblast cells, and rarely detected in trophoblastic syncytium. In all abnormal placentae, the LHRI of sinusoids was absent, and syncytium showed either enhanced (immature placental phenotypes) or no LHRI (aged placental phenotype). LHRI in human brain was identified in microglial cells (CD68+ resident macrophages). Protein extracts from human vaginal wall and levator ani muscle and fascia showed strong approximately 92 and 68 kDa species, and LHRI was detected in smooth muscle cells, fibroblasts, resident macrophages and nuclei of skeletal muscle fibers. Our observations indicate that, in contrast to the theory on the role of vascular hormone receptors in preferential pick up of circulating hormones, there is no need to enhance selective pick up rather only prevent LH/CG transport to inappropriate sites. Abnormal placental LHR expression may play a role in the development of abnormal pregnancy. Expression of LHR in the pelvic floor compartments suggests that high LH levels in postmenopausal women may contribute to the pelvic floor relaxation and increased incidence of pelvic floor disorders. Since chorionic gonadotropin increases secretion of a variety of cytokines by monocytes, and induces their inflammatory reaction and phagocytic activity, high LH levels in aging individuals may also activate microglia (mononuclear phagocyte system in the central nervous system) and contribute to the development of Alzheimer's disease and other inflammation-mediated neurodegenerative diseases.

Dual mechanisms of regulation of transcription of luteinizing hormone receptor gene by nuclear orphan receptors and histone deacetylase complexes

The luteinizing hormone receptor (LHR), a member of the G protein-coupled, seven transmembrane receptor family, is essential for normal sexual development and reproductive function. LHR are expressed primarily in the gonads, but also are found in non-gonadal and cancer tissues. LH acts through LH receptors in Leydig cells to maintain general metabolic processes and steroidogenic enzymes, and in the ovary enhances follicular development and steroidogenesis in granulosa and luteal cells. The major transcriptional start sites of the LHR gene are located within the 176bp promoter domain. In the rat, the LHR gene is constitutively inhibited by upstream sequences (-176/-2056bp) in several cell systems, while in the human only a minor inhibitory effect was observed in JAR and HeLa cells (>20%). The TATA-less human promoter is driven by Sp1 and Sp3 transactivators that bind to two Sp1 domains at -79bp [Sp1(I)] and -119bp [Sp1(II)] (from ATG) with additive effects. An imperfect estrogen receptor half-site response element direct-repeat within the LHR promoter is an inhibitory locus. Endogenous orphan receptors, EAR2 and EAR3/COUP-TFI, bind this motif and repress promoter activity by 70%. TR4 also binds this motif and stimulates promoter activity (up to 2.5-fold). This is reversed by coexpression of EAR2 or EAR3/COUP-TFI through competitive binding to this site. Comparative studies of hDR and rDR orphan receptors binding and function revealed sequence-specific requirements. The A/C mismatch between hDR and rDR is responsible for the lack of TR4 binding and function in the rat. The G 3'-adjacent to the hDR core is important for EAR2/EAR3-COUP-TFI high-affinity binding. The Sp1-1 site is critical for EAR3/COUP-TFI repression, with minor participation for EAR2, and is not involved in the TR4 effect. Interaction of EAR3/COUP-TFI with Sp1 perturbs association of TFIIB with Sp1, independently of HDACs, and caused impairment of LHR transcription. Other aspect of control is through HDAC/mSin3A mechanism. Inhibition of HDACs by TSA increases LHR promoter activity in JAR cells (40-fold), association of acetylated H3/H4 with the LHR promoter, recruitment of Pol II to the promoter, and LHR mRNA levels. A multiprotein complex is recruited to the hLHR promoter via interaction with Sp1/Sp3: HDACs dock directly to Sp1-1 bound DNA and indirectly to Sp3-1 bound DNA through RbAp48, while mSin3A interacts HDACs and potentiates HDAC1-mediated repression. Our studies have demonstrated that orphan receptor-ERE complexes, and the HDAC1-HDAC2-mSin3A complex have important roles in the regulation of LHR gene transcription by interaction with Sp1/Sp3, and by region-specific changes in histone acetylation and Pol II recruitment within the LHR promoter.

Messenger RNA expression for the follicle-stimulating hormone receptor and luteinizing hormone receptor in human oocytes and preimplantation-stage embryos

OBJECTIVE

To study the expression of the FSH and LH receptors in human oocytes and preimplantation embryos and their potential roles in early human development.

DESIGN

Clinical and molecular studies.

SETTING

University hospital IVF center.

PATIENT(S)

Female volunteers undergoing intracytoplasmic sperm injection at the IVF unit of the Athens University Hospital. All patients gave written informed consent.

INTERVENTION(S)

Ovarian stimulation was performed with exogenous gonadotropin administration. Intracytoplasmic sperm injection was performed on mature oocytes.

MAIN OUTCOME MEASURE(S)

Unfertilized oocytes and zygotes and embryos at the 2-cell, 4-cell, morula, and blastocyst stage were selected for study. A polymerase chain reaction methodology was used to analyze human oocytes and embryos. Messenger RNA was reverse transcribed and amplified with FSH and LH receptor specific primers.

RESULT(S)

Transcripts for the FSH receptor were detected in oocytes and zygotes and embryos at the 2-cell, morula, and blastocyst stage, while no message was detected in embryos at the 4-cell stage. Transcripts for the LH receptor were observed in oocytes and zygotes and morula- and blastocyst-stage embryos, whereas no message was detected in embryos at the 2-cell and 4-cell stage.

CONCLUSION(S)

Messenger RNA for the FSH and LH receptors was observed in oocytes and preimplantation embryos at different stages, indicating a physiological role in the oocyte maturation process and early embryonic development in the human.

Evidence for cycle-dependent expression of full-length human chorionic gonadotropin/luteinizing hormone receptor mRNA in human endometrium and decidua

OBJECTIVE

To investigate the expression of full-length and truncated hCG/LH-receptor mRNA in human endometrium and decidua.

DESIGN

In vitro experiment.

SETTING

Tertiary university center.

PATIENT(S)

Premenopausal women undergoing hysterectomy because of benign diseases or induced abortions.

INTERVENTION(S)

Isolation of RNA from endometrial samples, reverse transcription, selective preamplification of full-length hCG/LH receptor mRNA and several shorter fragments of the receptor gene (exons 1-11, 1-10, and 1-5), nested polymerase chain reaction with internal primers.

MAIN OUTCOME MEASURE(S)

Appropriately sized cDNA product confirmed by sequencing.

RESULT(S)

All samples derived from the proliferative as well as from the early and mid-luteal phases were positive for all four amplification products, suggesting the expression of a full-length hCG/LH receptor mRNA. Only 5 of 8 samples derived from the late secretory phase and 2 of 12 samples derived from early decidua amplified the entire receptor sequence. In contrast, the shortest fragment (exons 1-5), coding for part of the extracellular receptor domain, was amplified in all samples.

CONCLUSION(S)

The data suggest cycle-dependent regulation of hCG/LH-receptor mRNA by changes in the alternative splicing pattern and down-regulation of full-length hCG/LH receptor mRNA in early decidua. The major splicing site appears to be located between introns 5 and 9. Alternative splicing may be a mechanism regulating hCG/LH-receptor down-regulation.

Human chorionic gonadotropin (HCG) activates monocytes to produce interleukin-8 via a different pathway from luteinizing hormone/HCG receptor system

To investigate immune-endocrine interactions between the embryo and the mother early in pregnancy, we examined the effects of human chorionic gonadotropin (HCG) on IL-8 production by peripheral blood mononuclear cells (PBMC). Recombinant HCG promoted IL-8 secretion by PBMC derived from nonpregnant women. The induction of IL-8 mRNA expression was observed after 30 min of HCG stimulation. Adsorption of the HCG with anti-HCG antibodies confirmed the specificity of this effect. The translocation of nuclear factor kappaB into the nucleus and subsequent IL-8 production were observed mainly in monocytes, and IL-8 production was reduced when a proteasome inhibitor was added to inactivate nuclear factor kappaB. Although fluorescein isothiocyanate-labeled HCG was bound to the majority of monocytes, cell surface expression of HCG receptor was hardly detected. IL-8 production by HCG was not affected by inhibitors of protein kinases A and C. In contrast, this stimulation was attenuated by D-mannose, which inhibits binding to C-type lectins. The basal IL-8 production by PBMC from women early in pregnancy was significantly elevated, compared with that from nonpregnant women. This study showed that human monocytes respond to HCG and secrete IL-8 through a pathway different from the HCG receptor system, suggesting that this glycoprotein hormone can react with not only endocrine cells but also immune cells early in pregnancy, probably via primitive systems such as C-type lectins.

Human peripheral blood polymorphonuclear leukocytes at the ovulatory period are in an activated state

The ovulatory process has been compared with inflammation. We investigated the state of female peripheral polymorphonuclear leukocytes (PMN) during menstrual cycles, and found that PMN contained high levels of superoxide, hydrogen peroxide and nitric oxide (NO) during at the peri-ovulatory period. Assuming the cause of this elevation to be a luteinizing hormone (LH), the surge of which preceded the ovulation, we examined the responsiveness of PMN to pituitary LH. The results revealed that this hormone elevated dose-dependently the production of reactive oxygen intermediates (ROI). Furthermore, we demonstrated the mRNA expression of LH receptors and their presence on PMN. The data indicated that the LH surge before on the ovulatory day resulted in general activation of PMN, suggesting that this state of PMN may be a necessary step for initiation of ovulation, rather than a defensive role against infection.

Absence of activating mutations in the hot spots of the LH receptor and Gs-alpha genes in Leydig cell tumors

Leydig-cell tumors are functioning endocrine tumors that produce T autonomously leading to isosexual precocity in boys and virilization in female patients. Molecular abnormalities such as activating mutations of the luteinizing hormone receptor (LHR), a G protein-coupled receptor, and of the Gs-alpha subunit of G protein have recently been described in these tumors. Both mutations cause continuous activation of the cAMP signaling cascade, autonomous production of T and cell proliferation. We searched for activating mutations in exon 11 of the LHR gene and in exons 8 and 9 of the Gs-a gene, which contain all hot spots for those mutations, in 4 Leydig cell tumors obtained from 4 patients (one boy with LH-independent precocious puberty and 3 women with virilization). DNA was extracted from paraffin-embedded neoplastic and non-neoplastic tissues and from peripheral lymphocytes. Hot spot regions of exons 11 of LHR and exons 8 and 9 of Gs-alpha genes were amplified by PCR and the purified PCR products were directly sequenced. No LHR or Gs-alpha gene mutations were found in the 4 tumors studied. Considering the previously reported mutations found in Leydig cell tumors, the absence of activating mutations in the hot spot regions for activating mutations in these tumors indicate molecular heterogeneity among Leydig cell tumors.

Intracellular calcium mobilization in response to the activation of human wild-type and chimeric gonadotropin receptors

It is well established that LH action is mediated primarily by adenylate cyclase/cAMP. However, the role of inositol phosphate/calcium in LH signaling is less well established. We examined the effects of gonadotropins in primary culture human granulosa-lutein cells and in HEK293 cells transiently transfected with human wild-type or chimeric gonadotropin receptors. The intracellular free calcium concentration was measured using fura-2 microspectrofluorometric techniques. Human (h) LH (2-4 microg/ml) and CG (10 IU/ml) consistently evoked oscillatory calcium signals in HEK293 cells transfected with hLH receptor, whereas hFSH (2-4 microg/ml) failed to elicit any response. Conversely, both hLH and hFSH failed to elicit a calcium response from HEK293 cells transfected with hFSHR, indicating the specificity of the response to the LH receptor. Pretreatment of transfected HEK293 cells with pertussis toxin (100 ng/ml) attenuated all gonadotropin-evoked calcium mobilization. Studies with chimeric LH receptor showed that the sequence of the long extracellular portion of the receptor was not critical for stimulation of PLC activity, but maintained agonist binding specificity. The C-terminal sequence of the receptor was clearly important for the generation of the basal calcium oscillations, but the precise extent of the critical sequence has yet to be identified. Although various subdivisions of this region were capable of stimulating calcium transients, an intact carboxyl-terminal third of the receptor was required for normal and sustained intracellular calcium signaling. Our study unequivocally shows that the hLH receptor is coupled to the inositol phosphate/calcium signaling pathway via a pertussis toxin-sensitive G protein-coupled receptor.