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1.
J Clin Endocrinol Metab ; 86(10): 5060-6, 2001 Oct.
Article in English | MEDLINE | ID: mdl-11600585

ABSTRACT

It is currently believed that the postmenopausal ovary remains a gonadotropin-driven, androgen-producing gland. However, the adrenal contribution to circulating androgen levels may explain some conflicting results previously reported. In addition, the steroidogenic potential and gonadotropin responsiveness of the postmenopausal ovary have not been recently reassessed. Plasma T, bioavailable T, free T, androstenedione (Adione), and dehydroepiandrosterone sulfate levels were measured in postmenopausal or ovariectomized women with complete adrenal insufficiency, compared with women with intact adrenals. A stimulation human chorionic gonadotropin test (on d 0, 3, and 6) was performed in postmenopausal women with adrenal insufficiency. Dexamethasone was administered for 4 d in postmenopausal women with intact adrenals. Intraovarian T and androstenedione were also measured in homogenates of ovarian tissue from postmenopausal women. Immunocytochemistry was performed on postmenopausal ovaries and premenopausal controls to detect the presence of steroidogenic enzymes (P-450 aromatase, P-450 SCC, 3beta HSD, and P-450 C17) and gonadotropin receptors. Plasma androgen levels were below or close to the limit of the assay in all women with adrenal insufficiency. They were similar in postmenopausal and oophorectomized women with normal adrenals. No hormonal changes were observed after human chorionic gonadotropin injections in women with adrenal insufficiency. In contrast, a dramatic decrease of all steroids was observed after dexamethasone administration in postmenopausal women with intact adrenals. Intraovarian T and androstenedione levels were negligible in postmenopausal ovarian tissue. P-450 aromatase was absent from the 17 ovaries studied, and the enzymes for androgen biosynthesis were either absent (n = 13) or present in very low amounts (n = 4). In all the postmenopausal ovaries, FSH and LH receptors were completely absent. In the absence of adrenal steroids, postmenopausal women have no circulating androgens. This result is consistent with the immunocytochemical studies showing the almost constantly absent steroidogenic enzymes and LH receptors in the postmenopausal ovary. Thus, the climacteric ovary is not a critical source of androgens. The arrest of androgen secretion after menopause may impact significantly on women's health.


Subject(s)
Androgens/biosynthesis , Ovary/metabolism , Postmenopause/metabolism , Adrenal Glands/metabolism , Aged , Aromatase/metabolism , Dehydroepiandrosterone/blood , Female , Humans , Immunohistochemistry , Middle Aged , Ovary/chemistry , Receptors, FSH/analysis , Receptors, LH/analysis , Testosterone/analysis
2.
Semin Reprod Med ; 19(1): 97-101, 2001.
Article in English | MEDLINE | ID: mdl-11394210

ABSTRACT

Gonadotropins cross the vascular endothelial barrier to reach their target organs. Hormone concentrations in blood are very low and fluctuate rapidly to give sharp biological effects. Nonspecific transendothelial transport mechanisms are slow and markedly concentration dependent. There is thus a need for specific transendothelial transport mechanisms for these hormones. We will describe a specific transcytosis mechanism involving endothelial lutropin/chorionic gonadotropin (LH/CG) receptors identical to those observed in the target Leydig cells. A new role for the LH/CG receptor as a transcytotic carrier of its ligands in endothelial cells is suggested.


Subject(s)
Endothelium, Vascular/metabolism , Hormones/metabolism , Receptors, LH/physiology , Animals , Biological Transport , Chorionic Gonadotropin/metabolism , Humans , Leydig Cells/metabolism , Leydig Cells/ultrastructure , Male , Microscopy, Electron , Testis/blood supply
3.
Mol Cell Endocrinol ; 179(1-2): 83-7, 2001 Jun 20.
Article in English | MEDLINE | ID: mdl-11420132

ABSTRACT

Gonadotropin and GnRH receptors belong to the family of G protein coupled receptors. Gain of function mutations have been described, yielding constitutively active receptors. In the case of the LH receptor these dominant mutations determine familial male limited precocious puberty. Somatic mutations of this receptor may in some cases provoke Leydig-cell adenomas. The constitutive LH receptor is not associated with female precocious puberty. Inactivating mutations are recessive. Alterations in the GnRH receptor determine hypogonadotropic hypogonadism. The clinical diagnosis of this etiology of hypogonadism is extremely difficult, especially in sporadic cases. Mutations of gonadotropin receptors determine primary amenorrhea in girls, whereas in boys they are responsible for Leydig cell aplasia or hypoplasia (LH receptor) or of a variable alteration of spermatogenesis (FSH receptor). Mutations provoking only partial alterations of receptor functions are relatively more frequent, than those inducing complete receptor inactivity. They provide interesting insights into the physiology of GnRH and gonadotropin action.


Subject(s)
Gonadotropins/metabolism , Hypogonadism/physiopathology , Receptors, FSH/metabolism , Receptors, LHRH/metabolism , Receptors, LH/metabolism , Female , Humans , Hypogonadism/genetics , Male , Mutation/genetics , Receptors, FSH/genetics , Receptors, LH/genetics , Receptors, LHRH/genetics
4.
J Biol Chem ; 276(5): 3054-9, 2001 Feb 02.
Article in English | MEDLINE | ID: mdl-11042205

ABSTRACT

We have identified 7-ketocholesterol (7-KC) as an endogenous modulator that inhibits transactivation by the arylhydrocarbon receptor (AhR) through competitive binding against xenobiotic ligands. 7-KC binds AhR and displaces labeled dioxin (2,3,7,8-tetrachlorodibenzo(p)dioxin (TCDD)). IC(50) is 5 x 10(-7) m in vivo and 7 x 10(-6) m in vitro. These figures are consistent with its concentration in human blood plasma and tissues. Association with 7-KC prevents AhR binding to DNA. 7-KC blocks the TCDD-mediated transactivation of stably expressed reporter gene constructs in T47-D cells as well as the expression of the endogenous CYP 1A1 gene in HepG2 cells and in primary porcine aortic endothelial cells. Injection of 7-KC to rats blocks the induction of CYP 1A1 messenger RNA and protein in endothelial cells from myocardial blood vessels. The differential sensitivity of mammalian species to toxic effects of AhR ligands, especially dioxin (TCDD), correlates with the expression of 7-hydroxycholesterol dehydrogenase, which synthesizes 7-KC from 7-hydroxycholesterol. The documented involvement of AhR ligands in cardiovascular diseases through lipid peroxidation and endothelium dysfunction can now be examined in the context of displacement of this protective modulator.


Subject(s)
Ketocholesterols/metabolism , Receptors, Aryl Hydrocarbon/metabolism , Transcriptional Activation/physiology , Animals , Cytochrome P-450 CYP1A1/metabolism , Humans , Hydroxysteroid Dehydrogenases/metabolism , Ketocholesterols/physiology , Polychlorinated Dibenzodioxins/pharmacology , Rats , Receptors, Aryl Hydrocarbon/genetics , Teratogens/pharmacology , Transcriptional Activation/drug effects , Tumor Cells, Cultured
5.
Bull Acad Natl Med ; 184(3): 605-16; discussion 617-9, 2000.
Article in French | MEDLINE | ID: mdl-10989556

ABSTRACT

Mutations of receptor genes are involved in various aspects of thyroid and gonadal pathology. Activating mutations of TSH and LH receptors are associated with hyperthyroidism and premature puberty. These mutations are dominant and lead to the synthesis of a constitutive receptor, i.e. a receptor active even in the absence of hormone. Inactivating mutations of TSH, gonadotropin and GnRH receptors are recessive. They determine either a hypothyroidism or a hypogonadism. In the case of alterations of gonadotropin receptors the hypogonadism is hypergonadotrophic. It is hypogonadotrophic in the case of mutations of the GnRH receptor.


Subject(s)
Hyperthyroidism/etiology , Hypothyroidism/etiology , Puberty, Precocious/etiology , Receptors, LH/genetics , Receptors, Thyrotropin/genetics , Humans , Mutation
7.
Biochemistry ; 39(18): 5509-17, 2000 May 09.
Article in English | MEDLINE | ID: mdl-10820024

ABSTRACT

Our present knowledge of the lutropin (LH/hCG) receptor structure derives from deductions made from its amino acid sequence as established by studying the cDNA. To obtain direct experimental information, luteinizing hormone (LH) receptor expressed in L cells was immunopurified in sufficient amounts to warrant analysis by mass spectrometry and microsequencing. The mature receptor, complexed to human chorionic gonadotropin (hCG), was purified by using monoclonal antibodies recognizing the hormone, whereas the mannose-rich non-hormone-binding precursor was purified by use of antireceptor antibodies. Determination of the N-terminus showed that (2)/(3) of protein molecules started at Thr24 whereas (1)/(3) started at Ala28. All these molecules bound hCG, suggesting that the most N-terminal region of the receptor does not participate in hormone binding. Six N-glycosylation sites have been predicted from the amino acid sequence. One of them (Asn299) was found to be nonglycosylated in both the precursor and the mature protein. The most heavily glycosylated residue was Asn291, followed by Asn195 and Asn99. These three sites accounted for 82% and 97% of carbohydrate moieties in the mature receptor and in the mannose-rich precursor, respectively. The presence of some receptor molecules nonglycosylated at sites 99, 174, and 195 in hormone-receptor complexes dismisses a direct role of these glycosylation sites in hormone binding or in the correct folding of the protein. The mature carbohydrate chains were homogeneous at position 174, 195, and 313 (absence of Golgi mannosidase II activity at positions 174 and 313, absence of GlcNAc tranferases III and IV activity at position 195). Heterologous carbohydrates were present at sites 99 and 291. The latter, which is highly variable in carbohydrate chains, is unlikely to participate in a direct interaction with hormone. Site 313 thus remains as the main candidate for a role in hormone binding.


Subject(s)
Protein Precursors/chemistry , Protein Processing, Post-Translational , Receptors, LH/chemistry , Amino Acid Sequence , Animals , Carbohydrate Sequence , Chorionic Gonadotropin/metabolism , Chromatography, High Pressure Liquid , Glycosylation , L Cells , Mass Spectrometry , Mice , Molecular Sequence Data , Oligosaccharides/biosynthesis , Organophosphorus Compounds , Peptide Fragments/chemistry , Protein Binding , Protein Precursors/isolation & purification , Receptors, LH/isolation & purification , Sequence Analysis, Protein
8.
J Biol Chem ; 275(12): 8540-8, 2000 Mar 24.
Article in English | MEDLINE | ID: mdl-10722692

ABSTRACT

JAB1 (Jun activation domain-binding protein-1) has previously been described as a coactivator of AP1 transcription factor. We show here, by yeast and mammalian two-hybrid analyses and by pull-down experiments, that JAB1 also interacts with both the progesterone receptor (PR) and the steroid receptor coactivator 1 (SRC-1) and that it stabilizes PR-SRC-1 complexes. We also show that JAB1 potentiates the activity of a variety of transcription factors known to associate with SRC-1 (nuclear receptors, activator protein-1, and nuclear factor kappaB). This occurs without any modification of PR or SRC-1 concentration. JAB1 is a subunit of a large multiprotein complex that has been called the COP9 signalosome. The latter is present in plant and animal cells and has been shown to be involved in a variety of cellular mechanisms including transcription regulation, cell cycle control, and phosphorylation cascades. We now show that it is also involved in the mechanisms of action of nuclear receptors and of their coactivators.


Subject(s)
DNA-Binding Proteins/metabolism , Receptors, Progesterone/metabolism , Transcription Factors/metabolism , Binding Sites , DNA-Binding Proteins/genetics , Histone Acetyltransferases , Nuclear Receptor Coactivator 1 , Peptide Hydrolases , Protein Binding , Receptors, Cytoplasmic and Nuclear/metabolism , Receptors, Glucocorticoid/metabolism , Recombinant Proteins/metabolism , Signal Transduction , Transcription Factor AP-1/metabolism , Transcription Factors/genetics , Two-Hybrid System Techniques
9.
Gene ; 243(1-2): 195-205, 2000 Feb 08.
Article in English | MEDLINE | ID: mdl-10675628

ABSTRACT

We isolated a mutation (rlr1-1; required for lacZ RNA) in the Saccharomyces cerevisiae (Sc) RLR1 gene as a suppressor of sin4, a component of the Mediator subcomplex of the RNA polymerase II holoenzyme and a determinant of chromatin structure. RLR1 encodes a deduced protein found also in fission yeast, nematode worms, and humans. The presence of these orthologs suggests that Rlr1 family members comprise a class of putative KEKE motif-containing proteins, characteristic of certain chaperones as well as regulators and subunits of the mammalian 20S proteasome. A role for RLR1 (THO2) in transcription appears to occur at a step subsequent to transcription initiation (see also Piruat, J.I. and Aguilera, A., 1998. EMBO J. 17, 4859-4872); Sc genes fused to the reporter gene lacZ were expressed at a very low level, while the corresponding native chromosomal genes were expressed at approximately normal levels in rlr1 mutants. Our studies show that rlr1 mutations cause a wide range of growth defects in addition to their novel affect on lacZ.


Subject(s)
Cytochromes c , Fungal Proteins/genetics , Lac Operon/genetics , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/genetics , Trans-Activators , Transcription Factors/genetics , Amino Acid Sequence , Cell Division/genetics , Cloning, Molecular , Conserved Sequence , Cytochrome c Group/genetics , DNA, Fungal/chemistry , DNA, Fungal/genetics , Fungal Proteins/physiology , Gene Expression Regulation, Fungal/physiology , Humans , Mediator Complex , Molecular Sequence Data , Mutation , Phylogeny , Recombinant Fusion Proteins/genetics , Saccharomyces cerevisiae/growth & development , Sequence Alignment , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Spores, Fungal/genetics
10.
Br J Dermatol ; 141(3): 438-46, 1999 Sep.
Article in English | MEDLINE | ID: mdl-10583046

ABSTRACT

Two different monoclonal antibodies recognizing different epitopes were used to study the localization of luteinizing hormone/human chorionic gonadotrophin (LH/hCG) receptors in human skin. Immunolabelling was observed only in the epidermis and derived structures but not in the dermis. The basal, spinal and granular layers were stained, whereas no receptors were detected in the non-nucleated horny cells. In the growing (anagen) hair, immunostaining was found in the inner root sheath below the level of the sebaceous glands and in the outer root sheath above this level. In the resting (telogen) hair, only the latter staining was observed. In the sebaceous glands, only the thin cells close to the walls of the ducts were immunolabelled. In the eccrine sweat glands, the external clear cells were stained in the secretory portion of the gland, whereas only the cells close to the lumen were labelled in the ducts. The distribution of LH/hCG receptors was compared with that of steroidogenic enzymes (side chain cleavage cytochrome P450, adrenodoxin, 3-beta-hydroxy-5-ene steroid dehydrogenase Delta5-Delta4 isomerase, 17-hydroxylase cytochrome P450 and cytochrome P450 aromatase). Only partial overlaps were observed. The presence of LH receptor mRNA in the skin was confirmed by reverse transcription-polymerase chain reaction. Monoclonal antibodies raised against the human follicle-stimulating hormone receptor failed to detect the latter in the epidermal structures and in the dermis. The role of LH and hCG in skin modifications occurring during pregnancy and after the menopause is unknown. These hormones may possibly act by regulating steroidogenic enzymes or by modulating cell growth and differentiation.


Subject(s)
Receptors, LH/analysis , Skin/chemistry , Adult , Aged , Eccrine Glands/chemistry , Epidermis/chemistry , Female , Hair Follicle/chemistry , Humans , Immunohistochemistry , Male , Middle Aged , RNA, Messenger/analysis , Receptors, LH/genetics , Reverse Transcriptase Polymerase Chain Reaction , Sebaceous Glands/chemistry
11.
Mol Endocrinol ; 13(11): 1844-54, 1999 Nov.
Article in English | MEDLINE | ID: mdl-10551778

ABSTRACT

Premature ovarian failure occurs in almost 1% of women under age 40. Molecular alterations of the FSH receptor (FSHR) have recently been described. A first homozygous mutation of the FSHR was identified in Finland. More recently, we described two new mutations of the FSHR in a woman presenting a partial FSH-resistance syndrome (patient 1). We now report new molecular alterations of the FSHR in another woman (patient 2) who presented at the age of 19 with primary amenorrhea contrasting with normal pubertal development. She had high plasma FSH, and numerous ovarian follicles up to 3 mm in size were evidenced by ultrasonography. Histological and immunohistochemical examination of ovarian biopsies revealed the presence of a normal follicular development up to the antral stage and disruption at further stages. DNA sequencing showed two heterozygous mutations: Asp224Val in the extracellular domain and Leu601Val in the third extracellular loop of FSHR. Cells transfected with expression vectors encoding the wild type or the mutated Leu601Val receptors bound hormone with similar affinity, whereas binding was barely detectable with the Asp224Val mutant. Confocal microscopy showed the latter to have an impaired targeting to the cell membrane. This was confirmed by its accumulation as a mannose-rich precursor. Adenylate cyclase stimulation by FSH of the Leu601Val mutant receptor showed a 12+/-3% residual activity, whereas in patient 1 a 24+/-4% residual activity was detected for the Arg573Cys mutant receptor. These results are in keeping with the fact that estradiol and inhibin B levels were higher in patient 1 and that stimulation with recombinant FSH did not increase follicular size, estradiol, or inhibin B levels in patient 2 in contrast to what was observed for patient 1. Thus, differences in the residual activity of mutated FSHR led to differences in the clinical, biological, and histological phenotypes of the patient.


Subject(s)
Amenorrhea/genetics , Mutation , Ovary/physiopathology , Receptors, FSH/genetics , Adenylyl Cyclases/drug effects , Adenylyl Cyclases/metabolism , Adult , Amenorrhea/drug therapy , Animals , COS Cells/drug effects , COS Cells/metabolism , Female , Follicle Stimulating Hormone/pharmacology , Follicle Stimulating Hormone/therapeutic use , Gene Silencing , Humans , Immunohistochemistry , Male , Ovary/diagnostic imaging , Ovary/pathology , Phenotype , Primary Ovarian Insufficiency/drug therapy , Primary Ovarian Insufficiency/genetics , Protein Processing, Post-Translational , Receptors, FSH/drug effects , Receptors, FSH/metabolism , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Sequence Analysis , Ultrasonography
12.
Eur J Biochem ; 265(3): 1022-31, 1999 Nov.
Article in English | MEDLINE | ID: mdl-10518798

ABSTRACT

Native thyrotropin receptor (TSHR) was purified by immunoaffinity chromatography from membrane extracts of stably transfected L cells. An ELISA test was devised to study anti-TSHR autoantibodies directly. Comparison of native TSHR with bacterially expressed, denatured TSHR showed that the latter was not recognized by the autoantibodies, suggesting that they bind to conformational epitopes only present on the native receptor. The use of deglycosylated TSHR and of purified receptor ectodomain (alpha-subunit) showed that the autoantibodies recognized only the protein backbone moiety of the receptor and that their epitopes were localized entirely in its ectodomain. Autoantibodies were detected in 45 of 48 subjects with untreated Graves' disease and in 26 of 47 healthy volunteers. The affinity for the receptor was similar in the two groups (Kd = 0.25-1 x 10-10 M) and the autoantibodies belonged to the IgG class in all cases. Although the concentration of autoantibodies was higher in Graves' disease patients (3.50 +/- 0.36 mg.L-1) than in control subjects (1.76 +/- 0.21) (mean +/- SEM), there was an overlap between the groups. Receptor-stimulating autoantibodies (TSAb) were studied by measuring cAMP synthesis in stably transfected HEK 293 cells. Their characteristics (recognition of alpha-subunit, of deglycosylated TSHR, nonrecognition of bacterially expressed denatured receptor) were similar to those of the antibodies detected by the ELISA test. TSAb were only found in individuals with Graves' disease. The ELISA test measures total anti-TSHR antibodies, whereas the test using adenylate cyclase stimulation measures antibodies that recognize specific epitopes involved in receptor activation. Our observations thus disprove the hypothesis according to which Graves' disease is related to the appearance of anti-TSHR antibodies not present in normal subjects. Actually, anti-TSHR antibodies exist in many euthyroid subjects, in some cases even at concentrations higher than those found in patients with Graves' disease. What distinguishes the latter from normal subjects is the existence of subpopulation(s) of antibodies directed against specific epitope(s) of the receptor involved in its activation.


Subject(s)
Autoantibodies , Receptors, Thyrotropin/chemistry , Receptors, Thyrotropin/immunology , Animals , Autoantigens/chemistry , Autoantigens/genetics , Cell Line , Enzyme-Linked Immunosorbent Assay , Epitopes/chemistry , Epitopes/genetics , Escherichia coli/genetics , Glycosylation , Graves Disease/immunology , Humans , L Cells , Mice , Protein Structure, Quaternary , Receptors, Thyrotropin/genetics , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Transfection
13.
Mol Endocrinol ; 13(10): 1751-65, 1999 Oct.
Article in English | MEDLINE | ID: mdl-10517676

ABSTRACT

Scant information is available to date on the intracellular trafficking of the TSH receptor. In the present study we have used stably transfected L cells that express the TSH receptor, 225I-labeled TSH, and antireceptor antibodies as well as gold-conjugated antireceptor monoclonal antibodies and hormone. The latter allowed us to study, by electron microscopy, the cellular distribution and endocytosis of TSH receptor. The receptor was initially localized on the plasmalemma proper and in clathrin-coated pits but was excluded from smooth vesicles open to the cell surface. It was internalized through clathrin-coated vesicles. Constitutive endocytosis represented 10% of cell surface receptor molecules. Endocytosis was increased 3-fold by incubation with hormone. The majority of internalized receptor molecules (90%) was recycled to the cell surface, whereas the hormone was degraded in lysosomes. This recycling of receptor was inhibited by administration of monensin. Electron microscopic and confocal microscopic studies were repeated in primary cultures of human thyroid cells and showed a distribution, and endocytosis pathways, very similar to those observed in transfected L cells. A previous study has shown the LH receptor to be endocytosed in high proportion and to be degraded in lysosomes. Confocal microscopy and colocalization studies with transferrin receptor confirmed that the highly homologous LH and TSH receptors exhibit, when expressed in the same cells, very different cellular trafficking properties. The use of LH/TSH receptor chimeras showed that transmembrane-intracellular domains contain information orienting the protein toward recycling or degradative pathways. The extracellular domain seems to play a role in the extent of intemalization. These observations should now allow the identification of the molecular signals involved.


Subject(s)
Receptors, Thyrotropin/metabolism , Thyroid Gland/metabolism , Biological Transport , Cells, Cultured , Chorionic Gonadotropin/metabolism , Endocytosis , Humans , Iodine Radioisotopes , Microscopy, Confocal , Microscopy, Immunoelectron , Receptors, LH/metabolism , Receptors, Thyrotropin/genetics , Receptors, Thyrotropin/immunology , Receptors, Transferrin/metabolism , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Subcellular Fractions , Thyroid Gland/cytology , Thyrotropin/metabolism , Transfection
14.
J Soc Biol ; 193(3): 269-73, 1999.
Article in French | MEDLINE | ID: mdl-10542957

ABSTRACT

Steroid hormone receptors define a large family of proteins. Recently, a new estradiol receptor has been identified. This discovery suggests the existence of a previously unrecognized pathway of estrogen signalling. Moreover, it implies important pharmacological consequences. Receptors activation induces the modulation of transcription of specific genes. Proteins involved in this effect have been identified: coactivators, corepressors and cointegrators. Their mechanism of action have been characterized. They modify histone acetylation of the corresponding promotor. Sex steroid receptors are located in the nucleus. This nuclear localization is in fact a dynamic situation, resulting from a continuous shuttling of the receptor between the cytoplasm and the nucleus. Non genomic effects of steroids have also been described.


Subject(s)
Gonadal Steroid Hormones/physiology , Receptors, Steroid/physiology , Steroids/physiology , Animals , Cell Nucleus/physiology , Gene Expression Regulation , Humans , Promoter Regions, Genetic , Receptors, Steroid/genetics , Transcription, Genetic
15.
West J Med ; 171(1): 63, 1999 Jul.
Article in English | MEDLINE | ID: mdl-10483353
16.
Mol Pharmacol ; 56(4): 784-90, 1999 Oct.
Article in English | MEDLINE | ID: mdl-10496962

ABSTRACT

Aryl hydrocarbon receptor (AhR) ligands such as dioxin and benzo[a]pyrene are environmental contaminants with many adverse health effects, including immunosuppression, carcinogenesis, and endothelial cell damage. We show here that a wine component, resveratrol (3,5,4'-trihydroxystilbene), is a competitive antagonist of dioxin and other AhR ligands. Resveratrol promotes AhR translocation to the nucleus and binding to DNA at dioxin-responsive elements but subsequent transactivation does not take place. Resveratrol inhibits the transactivation of several dioxin-inducible genes including cytochrome P-450 1A1 and interleukin-1beta, both ex vivo and in vivo. Resveratrol has adequate potency and nontoxicity to warrant clinical testing as a prophylactic agent against aryl hydrocarbon-induced pathology.


Subject(s)
Anticarcinogenic Agents/pharmacology , Receptors, Aryl Hydrocarbon/antagonists & inhibitors , Stilbenes/pharmacology , Biological Transport/drug effects , Cell Nucleus/metabolism , Environmental Pollutants/pharmacology , Gene Expression Regulation/drug effects , Humans , Ligands , Polychlorinated Dibenzodioxins/pharmacology , Resveratrol , Transcriptional Activation/drug effects , Tumor Cells, Cultured
17.
Therapie ; 54(3): 327-31, 1999.
Article in French | MEDLINE | ID: mdl-10500446

ABSTRACT

Nuclear receptors form a superfamily of transcriptional regulators including both classical hormone receptors and orphan receptors. The functional anatomy of the receptors is described as well as their interaction with coactivators, cointegrators and corepressors. Nuclear receptors activate and inhibit gene transcription by regulating histone acetylases and histone deacetylases. Receptor isoforms (oestrogen receptors alpha and beta), ligands exerting differential effects on the same receptor and the mechanism of action of antihormones are discussed.


Subject(s)
Receptors, Cytoplasmic and Nuclear/physiology , Receptors, Estrogen/physiology , Animals , Estrogens/physiology , Humans , Receptors, Cell Surface/physiology , Transcription Factors/metabolism , Transcription, Genetic
18.
J Soc Biol ; 193(2): 139-45, 1999.
Article in French | MEDLINE | ID: mdl-10451347

ABSTRACT

Gonadotropin and TSH receptors belong to a subgroup of G protein-coupled receptors. TSH and FSH receptor present a particular intracellular traffic: they present a polarized basolateral expression in thyroid follicular cells and in Sertoli cells respectively. By contrast, the LH receptor is expressed circumferentially in target gonadic cells. We expressed these receptors in MDCK cells (a well characterized model of polarized epithelial cells) to understand this difference of properties. We show that the three receptors have a polarized basolateral expression in these cells. All contain a basolateral targeting signal. Furthermore, gonadotropin receptors undergo a partial transcytosis which is not observed for the TSH receptor. We show that heterotrimeric G proteins play a role in this mechanism of transcytosis. This effect is not mediated by adenylate cyclase activation and involves a population of G proteins different from that involved in signal transduction. We thus used in vitro mutagenesis to delineate the basolateral localization signal of the FSH receptor. Surprisingly, the signal is localized in the C-terminal tail of the intracellular domain which is not conserved between the three receptors. It contains 14 amino-acids and its activity is mainly dependent on a tyrosine and a leucine residue. The basolateral localization signal of the FSHR is not colinear with its internalization signal. This signal is autonomous and dominant because, when transferred to an apically targeted membrane protein, the neurotrophin receptor, it redirects the chimeric construct to the basolateral domain of MDCK cells. The basolateral localization signal of the FSH receptor is thus the first signal identified for a G protein-coupled receptor and more generally for a hormone receptor.


Subject(s)
Cell Membrane/metabolism , Ovarian Follicle/metabolism , Receptors, FSH/metabolism , Sertoli Cells/metabolism , Animals , Biological Transport , Cell Line , Cell Polarity , Female , GTP-Binding Proteins/metabolism , Male , Receptors, FSH/chemistry , Receptors, FSH/genetics , Receptors, LH/chemistry , Receptors, LH/genetics , Receptors, LH/metabolism , Receptors, Thyrotropin/chemistry , Receptors, Thyrotropin/genetics , Receptors, Thyrotropin/metabolism , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Signal Transduction , Transfection
19.
Ann Endocrinol (Paris) ; 60(2): 89-92, 1999 Jul.
Article in English | MEDLINE | ID: mdl-10456178

ABSTRACT

Gonadotropin receptors belong to a subgroup of G-protein coupled receptors characterized by a large extracellular domain responsible for the binding of the hormone. Soluble, hormone-binding, alternative splicing variants of the LH receptor, are present in high concentration. A mannose rich precursor form of LH and FSH receptor is accumulated inside target cells. FSH receptors are addressed to the basolateral domain of cells through specific signaling mechanisms. Gonadotropin receptors are also present in endothelial cells of target organ vessels and are involved in hormone transcytosis. Various genetic abnormalities of these receptors (and of the GnRH receptor) are discussed.


Subject(s)
Receptors, FSH , Receptors, LH , Animals , Humans , Receptors, FSH/analysis , Receptors, FSH/chemistry , Receptors, FSH/physiology , Receptors, LH/analysis , Receptors, LH/chemistry , Receptors, LH/physiology
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