The Experts below are selected from a list of 5781 Experts worldwide ranked by ideXlab platform
Martin Reincke - One of the best experts on this subject based on the ideXlab platform.
-
Clinical and molecular evidence for DAX-1 inhibition of steroidogenic factor-1-dependent ACTH Receptor gene expression.
European Journal of Endocrinology, 2005Co-Authors: Oliver Zwermann, Felix Beuschlein, Albrecht Klink, Enzo Lalli, Paolo Sassone-corsi, Martin ReinckeAbstract:BACKGROUND: The ACTH Receptor (ACTH-R) is a member of the seven transmembrane domain Receptor super-family. In non-functional adrenal adenomas and adrenocortical carcinomas, ACTH-R expression is low. However, no inhibitory factor for ACTH-R expression has been defined to date. DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1) is a general repressor of steroid production, inhibiting steroidogenic factor-1 (SF-1)-dependent expression of multiple steroidogenic enzymes. The aim of this study was to investigate whether ACTH-R gene transcription is affected by DAX-1 and whether this mechanism is involved in down-regulation of ACTH-R expression in adrenocortical tumors. METHODS: We screened 22 adrenocortical tumors for ACTH-R and DAX-1 mRNA expression by Northern blot. For in vitro analyses we co-transfected mouse Y1 adrenocortical carcinoma cells with the luciferase reporter gene vector pGL3 containing full-length constructs of human (h) or mouse (m) ACTH-R promoter together with a DAX-1 expression plasmid. These experiments were also performed using ACTH-R promoter 5'-deletion constructs and constructs mutated at the SF-1-binding sites. RESULTS: We found a negative correlation between DAX-1 and ACTH-R mRNA expression (R=-0.47, P
-
The –2 basepair initiation start site ACTH Receptor polymorphism influences ACTH induced adrenal androgen secretion
Experimental and Clinical Endocrinology & Diabetes, 2005Co-Authors: Nicole Reisch, Marc Slawik, Oliver Zwermann, F Beuschlein, Martin ReinckeAbstract:Dehydroepiandrosterone (DHEA) and its sulfate ester (DHEAS) are the most abundant steroids in human circulation. Adrenocorticotropic hormone (ACTH) is the primary secretagogue stimulating adrenal androgens (AA) secretion. Yet, genetic and environmental factors are assumed to play a determinant role in the regulation of their biosynthesis and, thus, might explain the high variability of AA levels. We recently reported a polymorphism within the transcription initiation site of the ACTH Receptor promoter gene altering the consensus sequence from CTC to CCC at –2bp which results in lower promoter activity in vitro and is associated with impaired cortisol response to ACTH stimulation in vivo. Here we show that this polymorphism also affects ACTH dependent AA secretion. We studied 14 normal volunteers: 6 CCC/CCC carriers and 8 CTC/CTC carriers of the ACTH Receptor polymorphism. Baseline DHEA concentrations did not differ between groups. However, in a 6 hour ACTH stimulation test with increasing ACTH1–24 doses (120 to 3860 ng/mbody surface area/h), CCC/CCC carriers showed a significantly lower DHEA response compared to CTC/CTC carriers (area under the curve: 3201±358 vs. 5586±842µg/ml*min, P
-
Genetic influence of an ACTH Receptor promoter polymorphism on adrenal androgen secretion
European journal of endocrinology, 2005Co-Authors: Nicole Reisch, Felix Beuschlein, Marc Slawik, Oliver Zwermann, Martin ReinckeAbstract:Objective: Adrenocorticotropic hormone (ACTH) is the primary secretagogue stimulating secretion of adrenal androgens (AA). Yet, genetic and environmental factors are assumed to play a determining role in the regulation of their biosynthesis and thus might explain the high variability of AA levels. Here we investigate the influence of an ACTH Receptor promoter polymorphism affecting ACTH Receptor gene transcription on ACTH-dependent dehydroepiandrosterone (DHEA) secretion. Design: We recently reported a polymorphism within the transcription initiation site of the ACTH Receptor gene promoter that alters the consensus sequence from CTC to CCC at 22bp. This results in lower promoter activity in vitro and is associated with impaired cortisol response to ACTH stimulation in vivo. We now studied 14 normal, lean volunteers aged 20‐35 years (eight CTC/CTC and six CCC/CCC carriers) in a 6-h ACTH stimulation test. Methods: After overnight dexamethasone suppression, ACTH1-24 was administered continuously in each subject with hourly increasing doses (120‐3840ng/m 2 body surface area/h) within a 6-h period. On a separate day, baseline DHEA samples were collected. Results: In the 6-h ACTH stimulation test, CTC/CTC carriers showed a significantly higher DHEA response than CCC/CCC carriers (area under the curve: 19367^2919 vs 11098^1241nmol/l per min; P , 0.04, Mann‐Whitney U-test). In contrast, baseline DHEA concentrations did not differ between groups. Conclusion: These data demonstrate that genetic variations within the ACTH Receptor promoter result in decreased DHEA secretion. Thus, we might have identified one of the genetic factors responsible for variation in ACTH-dependent DHEA secretion. European Journal of Endocrinology 153 711‐715
-
Clinical and molecular evidence for DAX-1 inhibition of steroidogenic factor-1-dependent ACTH Receptor gene expression.
European journal of endocrinology, 2005Co-Authors: Oliver Zwermann, Felix Beuschlein, Albrecht Klink, Enzo Lalli, Paolo Sassone-corsi, Martin ReinckeAbstract:Background: The ACTH Receptor (ACTH-R) is a member of the seven transmembrane domain Receptor super-family. In non-functional adrenal adenomas and adrenocortical carcinomas, ACTH-R expression is low. However, no inhibitory factor for ACTH-R expression has been defined to date. DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1) is a general repressor of steroid production, inhibiting steroidogenic factor-1 (SF-1)-dependent expression of multiple steroidogenic enzymes. The aim of this study was to investigate whether ACTH-R gene transcription is affected by DAX-1 and whether this mechanism is involved in down-regulation of ACTH-R expression in adrenocortical tumors. Methods: We screened 22 adrenocortical tumors for ACTH-R and DAX-1 mRNA expression by Northern blot. For in vitro analyses we co-transfected mouse Y1 adrenocortical carcinoma cells with the luciferase reporter gene vector pGL3 containing full-length constructs of human (h) or mouse (m) ACTH-R promoter together with a DAX-1 expression plasmid. These experiments were also performed using ACTH-R promoter 5 0 -deletion constructs and constructs mutated at the SF-1-binding sites. Results: We found a negative correlation between DAX-1 and ACTH-R mRNA expression (R ¼ 2 0.47, P , 0.02). Accordingly, in vitro expression of DAX-1 significantly reduced hACTH-R and mACTH-R promoter activity by 89 and 55% respectively. DAX-1 inhibition was also present in the shortest construct of a series of 5 0 -deletion constructs of the human promoter extending from 2 64 to þ 40 bp relative to the transcription start site. Mutation of the SF-1-binding sites within the hACTH-R promoter resulted in reduced or abolished DAX-1 inhibition, arguing for a mechanism that involves SF-1 for DAX-1 inhibition. Conclusions: These data support the concept that DAX-1 is a major repressor of ACTH-R gene expression in vitro and in vivo.
-
The role of the ACTH Receptor in adrenal tumors: identification of a novel microsatellite marker.
Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme, 2004Co-Authors: Oliver Zwermann, F Beuschlein, A. Klink, M. Stahl, Martin ReinckeAbstract:In vitro, the growth inhibiting effect of ACTH on adrenocortical cells is well documented, even though there are reports of opposite effects under defined cell culture conditions. In vivo, activation of the ACTH Receptor (ACTHR) has a trophic effect on the adrenal cortex, while the effects on proliferation are still under discussion, especially since other POMC derived peptides have been characterized. However, ACTH is thought to act as a differentiation factor with inhibiting effects on tumor growth. In undifferentiated adrenocortical carcinomas, ACTHR expression is frequently lost, which is associated with extensive tumor growth. We describe a new microsatellite marker within the intron of the ACTHR gene termed ACTHRint1. In a series of 114 patients with various adrenal and non-adrenal tumors, the rate of heterozygosity was 100 %. Only one out of 57 patients with adrenocortical adenoma showed LOH at the ACTHR locus, whereas 4 of 10 carcinomas had loss of one allele. Patients suffering from tumors with LOH showed a more aggressive disease course and had earlier recurrences with poor prognosis. These data confirm earlier findings that adrenocortical carcinomas frequently show loss of ACTHR expression, which is associated with a more aggressive tumor growth. However, whether the ACTHR is directly involved in tumor growth or acts a marker of differentiation that is lost in more advanced tumor stages is still not clear.
Martine Begeot - One of the best experts on this subject based on the ideXlab platform.
-
Compound heterozygosity of a frameshift mutation in the coding region and a single base substitution in the promoter of the ACTH Receptor gene in a family with isolated glucocorticoid deficiency.
Journal of pediatric endocrinology & metabolism : JPEM, 2006Co-Authors: P. Tsiotra, Danielle Naville, Martine Begeot, Sotirios A. Raptis, Athina Koukourava, Valeria Kaltezioti, Mitchell E. Geffner, Constantine TsigosAbstract:Isolated glucocorticoid deficiency (IGD) is an autosomal recessive syndrome characterized by glucocorticoid insufficiency without mineralocorticoid deficiency. Mutations in the coding region of the ACTH Receptor (MC2R) have been reported in several families with IGD. We amplified and sequenced the entire MC2R coding region in a new family with IGD. The proband was found to be heterozygous (paternal allele) for the mutation Gly217fs, which changes the open reading frame of the MC2R protein resulting in a truncated Receptor. No other abnormality was found in the MC2R coding region. However, sequencing of the promoter region of the MC2R gene (-1017/44 bp) of the proband revealed a heterozygous T-->C substitution in the maternal allele at -2 bp position from initiation of the transcription start site. This substitution was found in only 6.5% in a healthy unrelated population. Constructs containing this polymorphism consistently showed a significant 15% decrease in promoter activity compared to wild type. In conclusion, we provide evidence that the IGD in this previously unreported family with ACTH resistance appears to be secondary to compound heterozygosity of a coding region and a promoter mutation in the MC2R gene.
-
Mutations in MRAP, encoding a new interacting partner of the ACTH Receptor, cause familial glucocorticoid deficiency type 2.
Nature genetics, 2005Co-Authors: Louise A. Metherell, Danielle Naville, Martine Begeot, J. Paul Chapple, Sadani N. Cooray, Alessia David, Christian Becker, Franz Rüschendorf, Bernard Khoo, Peter NürnbergAbstract:Familial glucocorticoid deficiency (FGD), or hereditary unresponsiveness to adrenocorticotropin (ACTH; OMIM 202200), is an autosomal recessive disorder resulting from resistance to the action of ACTH on the adrenal cortex, which stimulates glucocorticoid production. Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood. Mutations of the ACTH Receptor (melanocortin 2 Receptor, MC2R) account for approximately 25% of cases of FGD. FGD without mutations of MC2R is called FGD type 2. Using SNP array genotyping, we mapped a locus involved in FGD type 2 to chromosome 21q22.1. We identified mutations in a gene encoding a 19-kDa single-transmembrane domain protein, now known as melanocortin 2 Receptor accessory protein (MRAP). We show that MRAP interacts with MC2R and may have a role in the trafficking of MC2R from the endoplasmic reticulum to the cell surface.
-
Exclusion of the Adrenocorticotropin (ACTH) Receptor (MC2R) Locus in Some Families with ACTH Resistance but No Mutations of the MC2R Coding Sequence (Familial Glucocorticoid Deficiency Type 2)
The Journal of clinical endocrinology and metabolism, 1998Co-Authors: Danielle Naville, Adrian J L Clark, A. Weber, Philippe Durand, Emmanuelle Génin, Martine BegeotAbstract:Several mutations in the coding exon of the ACTH Receptor (MC2R) gene have been reported in cases of familial glucocorticoid deficiency or FGD. However, many patients with a similar syndrome do not present any mutation in the coding region of this gene. This is the case in 11 families we have investigated. Patients in these families present the typical clinical features of FGD, but no mutation was found in the coding exon of the ACTH Receptor. To determine whether mutations on MC2R gene, but outside the coding region, may be involved in FGD in these families, we have performed a linkage analysis. Using three markers flanking MC2R gene on chromosome 18, we were able to exclude linkage in a region of 12 centimorgans around the gene. This result clearly indicates that FGD is genetically heterogeneous. Defects in gene(s) different from MC2R gene are implicated in this syndrome.
-
A steroidogenic factor-1 binding element is essential for basal human ACTH Receptor gene transcription.
Biochemical and biophysical research communications, 1998Co-Authors: Réjane Marchal, Danielle Naville, Martine Begeot, Philippe Durand, Armelle PenhoatAbstract:Abstract We have previously shown that the promoter of the human ACTH Receptor (ACTH-R) contains, at −35 bp, a binding site for the steroidogenic factor 1 (SF-1), an orphan nuclear Receptor which could be responsible for the transcriptional activity of this promoter. In the present study, electrophoretic mobility shift assays demonstrated that the sequence −43/−19 bound the SF-1 protein present in the nuclear extracts of adrenocortical cells. Mutation of the SF-1 binding site markedly reduced (40%) the basal transcription of the reporter gene in Y-1 cells transfected with the mutated p(−56/+22)GH construct compared to the wild-type construct. These results demonstrate that the SF-1 binding element present in this fragment is required for the basal promoter activity of the human ACTH-R gene. In addition, other binding elements located upstream from this characterized SF-1 binding site are involved in the full basal promoter activity of the human ACTH-R since transfection studies with a longer p(−1017/+22)GH construct resulted in a higher GH release than with the p(−56/+22)GH construct.
-
Stable expression of normal and mutant human ACTH Receptor: Study of ACTH binding and coupling to adenylate cyclase
Molecular and cellular endocrinology, 1997Co-Authors: Danielle Naville, L. Barjhoux, C. Jaillard, Philippe Durand, José M. Saez, Martine BegeotAbstract:Abstract Point mutations of the human ACTH Receptor have been reported in some patients with a familial glucocorticoid deficiency syndrome. To demonstrate that these mutations were responsible for the disease, it was necessary to develop a model in which characteristics of normal and mutant Receptors could be studied. We have developed a stable expression model in order to characterize the human ACTH Receptor by binding studies and functional coupling to adenylate cyclase. After confirmation of the stable integration of Receptor constructs, ACTH dose-responses for the production of cAMP were carried out. The EC50 for ACTH were 2.9±0.2×10−10 M and 2.4±0.8×10−10 M, respectively, for two different clones stably expressing the normal human ACTH Receptor. EC50 calculated for clones expressing either one of the two studied mutant Receptors (C251F and D107N) were increased: 4.1±0.9×10−9 M and 6.4±1.3×10−9 M respectively. These values were similar to that obtained with M3 parental cells (4.7±0.8×10−9 M). Binding studies were performed on the same clones. Scatchard analysis showed that clones expressing the normal Receptor possessed high affinity binding sites for ACTH, with Kd=5.8±2.4×10−10 M and 6.9±3.6×10−10 M, respectively, for the two different studied clones. A second type of sites, with low affinity (Kd around 10−8 M), was also present. There was no ACTH binding to the high affinity binding sites for the two clones expressing either one of the mutant Receptors. An impaired binding of ACTH to its Receptors is then responsible for the absence of biological response to ACTH in patients carrying these mutant ACTH Receptors.
Adrian J L Clark - One of the best experts on this subject based on the ideXlab platform.
-
Stability and Turnover of the ACTH Receptor Complex.
Frontiers in Endocrinology, 2019Co-Authors: Adrian J L Clark, Li F ChanAbstract:Glucocorticoid production in mammals is principally regulated by the action of the pituitary hormone adrenocorticotropin (ACTH) acting on its cognate membrane Receptor on the zona fasciculata cells of the adrenal cortex. The Receptor for ACTH consists of two essential components, a small seven transmembrane domain G protein-coupled Receptor of the melanocortin Receptor subgroup known as the melanocortin 2 Receptor (MC2R) and a small single transmembrane domain protein that adopts a antiparallel homodimeric form and which is known as the melanocortin 2 Receptor accessory protein (MRAP). MRAP is essential for the trafficking of the MC2R to the cell surface as well as being required for Receptor responsiveness to ACTH at physiological concentrations – probably by facilitating ACTH binding, but possibly also by supporting G protein interaction with the MC2R. A number of studies have shown that ACTH stimulates the expression of functional Receptor at the cell surface and the transcription of both MC2R and MRAP mRNA. However the time course of these transcriptional effects differs such that MRAP is expressed relatively rapidly whereas MC2R transcription responds much more slowly. Furthermore, recent data suggests that MRAP protein is turned over with a short half-life whereas MC2R has a significantly longer half-life. These findings imply that these two ACTH Receptor proteins have distinct trajectories and that it is likely that MRAP-independent MC2R is present at the cell surface. In such a situation newly transcribed and translated MRAP could enable the rapid recruitment of functional Receptor at the plasma membrane without the need for new MC2R translation. This may be advantageous in circumstances of significant stress in that the potentially complex and perhaps inefficient process of de novo MC2R translation, folding, post-translational modification and trafficking can be avoided.
-
Melanocortin 4 Receptor becomes an ACTH Receptor by coexpression of melanocortin Receptor accessory protein 2.
Molecular endocrinology (Baltimore Md.), 2013Co-Authors: Maria Josep Agulleiro, Adrian J L Clark, Raúl Cortés, Begoña Fernández-durán, S. Navarro, Raúl Guillot, Eirini Meimaridou, José Miguel Cerdá-reverterAbstract:Melanocortin 2 Receptor (MC2R) is the only canonical ACTH Receptor. Its functional expression requires the presence of an accessory protein, known as melanocortin Receptor 2 accessory protein 1 (MRAP1). The vertebrate genome exhibits a paralogue gene called MRAP2, which is duplicated in zebrafish (MRAP2a and MRAP2b), although its function remains unknown. In this paper, we demonstrate that MRAP2a enables MC4R, a canonical MSH Receptor, to be activated by ACTH with a similar sensitivity to that exhibited by MC2R. Both proteins physically interact and are coexpressed in the neurons of the preoptic area, a key region in the control of the energy balance and hypophyseal secretion in fish. ACTH injections inhibit food intake in wild-type zebrafish but not in fish lacking functional MC4R. Both MRAP1 and MRAP2a are hormonally regulated, suggesting that these proteins are substrates for feed-back regulatory pathways of melanocortin signaling. Fasting has no effect on the central expression of MRAP2a but stimulates MRAP2b expression. This protein interacts and is colocalized with MC4R in the tuberal hypothalamic neurons but has no effect on the pharmacologic profile of MC4R. However, MRPA2b is able to decrease basal reporter activity in cell lines expressing MC4R. It is plausible that MRAP2b decreases the constitutive activity of the MC4R during fasting periods, driving the animal toward a positive energy balance. Our data indicate that MRAP2s control the activity of MC4R, opening up new pathways for the regulation of melanocortin signaling and, by extension, for the regulation of the energy balance and obesity.
-
Homozygous nonsense and frameshift mutations of the ACTH Receptor in children with familial glucocorticoid deficiency (FGD) are not associated with long-term mineralocorticoid deficiency.
Clinical endocrinology, 2009Co-Authors: Li F Chan, Martin O. Savage, Louise A. Metherell, Heiko Krude, Colin Ball, Stephen M. P. O'riordan, Colm Costigan, Sally Ann Lynch, Paolo Cavarzere, Adrian J L ClarkAbstract:Summary Objective Familial glucocorticoid deficiency (FGD) is a rare auto- somal recessive disease characterized by isolated glucocorticoid deficiency with preserved mineralocorticoid secretion. Mutations in the ACTH Receptor (MC2R) account for approximately 25% of all FGD cases, but since these are usually missense mutations, a degree of Receptor function is frequently retained. A recent report, however, suggested that disturbances in the renin-aldosterone axis were seen in some patients with potentially more severe MC2R mutations. Furthermore, MC2R knock out mice have overt aldosterone deficiency and hyperkalaemia despite preservation of a normal zona glomerulosa. We wished to determine whether a group of patients with severe nonsense mutations of the MC2R exhibited evidence of mineralocorticoid deficiency, thereby challenging the conventional diagnostic feature of FGD which might result in diagnostic misclassification. Design Clinical review of patients with nonsense MC2R mutations. Patients Between 1993 and 2008, 164 patients with FGD were screened for mutations in the MC2R. Totally 42 patients (34 families) were found to have mutations in the MC2R. Of these, 6 patients (4 families) were found to have homozygous nonsense or frameshift mutations. Results Mild disturbances in the renin-angiotensin-aldosterone axis were noted in four out of six patients, ranging from slightly elevated plasma renin levels to low aldosterone levels, although frank mineralocorticoid deficiency or electrolyte disturbance were not found. No patient required fludrocortisone replacement. Conclusion Severe nonsense and frameshift MC2R mutations are not associated with clinically significant mineralocorticoid deficiency and are thus unlikely to require long-term mineralocorticoid replacement.
-
Constitutive activation of the human ACTH Receptor resulting from a synergistic interaction between two naturally occurring missense mutations in the MC2R gene.
Molecular and cellular endocrinology, 2004Co-Authors: Francesca Swords, Luke A Noon, Peter J King, Adrian J L ClarkAbstract:Two mutations in the same allele of the ACTH Receptor (melanocortin 2 Receptor, MC2R) associated with clinical hypersensitivity to ACTH have been described in a single case report. Using a stable Y6 cell expression system, we demonstrate that either the C21R or S247G mutations alone produce an inactive Receptor with loss of ligand binding and responsiveness. However, the presence of both mutations in the same molecule leads to a Receptor with a highly significant elevation in constitutive activity (basal cAMP accumulation for wild type expressing cells 199 +/- 11 pmol/mg protein; double mutant: 374 +/- 29 pmol/mg protein, P < 0.005. The co-expression of the normal MC2R allele results in the retention of a normal dose response to ACTH despite the presence of constitutive activity.
-
Expression, desensitization, and internalization of the ACTH Receptor (MC2R).
Annals of the New York Academy of Sciences, 2003Co-Authors: Adrian J L Clark, Luke A Noon, Asma H. Baig, Francesca Swords, László Hunyady, Peter J KingAbstract:: Research into the functions and mechanisms of action of the melanocortin 2 Receptor (MC2R) has been severely hampered by difficulties in expressing this gene in heterologous cells. This probably arises because of the need for a cofactor for cell surface expression. Using either the Y1 cell line that expresses endogenous MC2R or the Y6 cell line that expresses this putative expression factor, we have explored the mechanisms of desensitization and internalization after agonist stimulation. Protein kinase A dependence of desensitization has been demonstrated, although internalization is apparently independent of this kinase and dependent on a G protein Receptor kinase. Possible underlying reasons for this paradox are discussed.
Danielle Naville - One of the best experts on this subject based on the ideXlab platform.
-
Compound heterozygosity of a frameshift mutation in the coding region and a single base substitution in the promoter of the ACTH Receptor gene in a family with isolated glucocorticoid deficiency.
Journal of pediatric endocrinology & metabolism : JPEM, 2006Co-Authors: P. Tsiotra, Danielle Naville, Martine Begeot, Sotirios A. Raptis, Athina Koukourava, Valeria Kaltezioti, Mitchell E. Geffner, Constantine TsigosAbstract:Isolated glucocorticoid deficiency (IGD) is an autosomal recessive syndrome characterized by glucocorticoid insufficiency without mineralocorticoid deficiency. Mutations in the coding region of the ACTH Receptor (MC2R) have been reported in several families with IGD. We amplified and sequenced the entire MC2R coding region in a new family with IGD. The proband was found to be heterozygous (paternal allele) for the mutation Gly217fs, which changes the open reading frame of the MC2R protein resulting in a truncated Receptor. No other abnormality was found in the MC2R coding region. However, sequencing of the promoter region of the MC2R gene (-1017/44 bp) of the proband revealed a heterozygous T-->C substitution in the maternal allele at -2 bp position from initiation of the transcription start site. This substitution was found in only 6.5% in a healthy unrelated population. Constructs containing this polymorphism consistently showed a significant 15% decrease in promoter activity compared to wild type. In conclusion, we provide evidence that the IGD in this previously unreported family with ACTH resistance appears to be secondary to compound heterozygosity of a coding region and a promoter mutation in the MC2R gene.
-
Mutations in MRAP, encoding a new interacting partner of the ACTH Receptor, cause familial glucocorticoid deficiency type 2.
Nature genetics, 2005Co-Authors: Louise A. Metherell, Danielle Naville, Martine Begeot, J. Paul Chapple, Sadani N. Cooray, Alessia David, Christian Becker, Franz Rüschendorf, Bernard Khoo, Peter NürnbergAbstract:Familial glucocorticoid deficiency (FGD), or hereditary unresponsiveness to adrenocorticotropin (ACTH; OMIM 202200), is an autosomal recessive disorder resulting from resistance to the action of ACTH on the adrenal cortex, which stimulates glucocorticoid production. Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood. Mutations of the ACTH Receptor (melanocortin 2 Receptor, MC2R) account for approximately 25% of cases of FGD. FGD without mutations of MC2R is called FGD type 2. Using SNP array genotyping, we mapped a locus involved in FGD type 2 to chromosome 21q22.1. We identified mutations in a gene encoding a 19-kDa single-transmembrane domain protein, now known as melanocortin 2 Receptor accessory protein (MRAP). We show that MRAP interacts with MC2R and may have a role in the trafficking of MC2R from the endoplasmic reticulum to the cell surface.
-
Functional expression of the human ACTH Receptor gene.
Endocrine research, 2000Co-Authors: Armelle Penhoat, Danielle Naville, H. El Mourabit, A. Buronfosse, Ph. Durand, M BégeotAbstract:The ACTH Receptor is the type 2 (MC2R) among the melanocortin Receptor family and is expressed almost exclusively in the adrenal cortex. The human MC2R (hMC2R) was very difficult to express in heterologous cell lines. We have succeeded in transient and stable expression of hMC2R using the M3 melanoma cells. Moreover, we have found that the expressed hMC2R in M3 cells showed similar ACTH binding affinity and coupling to adenylate cyclase as the MC2R of normal human adrenal cells, contrarily to most of the other expression cell models. In these conditions, we have been able to test several mutant hMC2R described in patients with the familial glucocorticoid deficiency syndrome (FGD) using this cell line.
-
Exclusion of the Adrenocorticotropin (ACTH) Receptor (MC2R) Locus in Some Families with ACTH Resistance but No Mutations of the MC2R Coding Sequence (Familial Glucocorticoid Deficiency Type 2)
The Journal of clinical endocrinology and metabolism, 1998Co-Authors: Danielle Naville, Adrian J L Clark, A. Weber, Philippe Durand, Emmanuelle Génin, Martine BegeotAbstract:Several mutations in the coding exon of the ACTH Receptor (MC2R) gene have been reported in cases of familial glucocorticoid deficiency or FGD. However, many patients with a similar syndrome do not present any mutation in the coding region of this gene. This is the case in 11 families we have investigated. Patients in these families present the typical clinical features of FGD, but no mutation was found in the coding exon of the ACTH Receptor. To determine whether mutations on MC2R gene, but outside the coding region, may be involved in FGD in these families, we have performed a linkage analysis. Using three markers flanking MC2R gene on chromosome 18, we were able to exclude linkage in a region of 12 centimorgans around the gene. This result clearly indicates that FGD is genetically heterogeneous. Defects in gene(s) different from MC2R gene are implicated in this syndrome.
-
A steroidogenic factor-1 binding element is essential for basal human ACTH Receptor gene transcription.
Biochemical and biophysical research communications, 1998Co-Authors: Réjane Marchal, Danielle Naville, Martine Begeot, Philippe Durand, Armelle PenhoatAbstract:Abstract We have previously shown that the promoter of the human ACTH Receptor (ACTH-R) contains, at −35 bp, a binding site for the steroidogenic factor 1 (SF-1), an orphan nuclear Receptor which could be responsible for the transcriptional activity of this promoter. In the present study, electrophoretic mobility shift assays demonstrated that the sequence −43/−19 bound the SF-1 protein present in the nuclear extracts of adrenocortical cells. Mutation of the SF-1 binding site markedly reduced (40%) the basal transcription of the reporter gene in Y-1 cells transfected with the mutated p(−56/+22)GH construct compared to the wild-type construct. These results demonstrate that the SF-1 binding element present in this fragment is required for the basal promoter activity of the human ACTH-R gene. In addition, other binding elements located upstream from this characterized SF-1 binding site are involved in the full basal promoter activity of the human ACTH-R since transfection studies with a longer p(−1017/+22)GH construct resulted in a higher GH release than with the p(−56/+22)GH construct.
Felix Beuschlein - One of the best experts on this subject based on the ideXlab platform.
-
Clinical and molecular evidence for DAX-1 inhibition of steroidogenic factor-1-dependent ACTH Receptor gene expression.
European Journal of Endocrinology, 2005Co-Authors: Oliver Zwermann, Felix Beuschlein, Albrecht Klink, Enzo Lalli, Paolo Sassone-corsi, Martin ReinckeAbstract:BACKGROUND: The ACTH Receptor (ACTH-R) is a member of the seven transmembrane domain Receptor super-family. In non-functional adrenal adenomas and adrenocortical carcinomas, ACTH-R expression is low. However, no inhibitory factor for ACTH-R expression has been defined to date. DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1) is a general repressor of steroid production, inhibiting steroidogenic factor-1 (SF-1)-dependent expression of multiple steroidogenic enzymes. The aim of this study was to investigate whether ACTH-R gene transcription is affected by DAX-1 and whether this mechanism is involved in down-regulation of ACTH-R expression in adrenocortical tumors. METHODS: We screened 22 adrenocortical tumors for ACTH-R and DAX-1 mRNA expression by Northern blot. For in vitro analyses we co-transfected mouse Y1 adrenocortical carcinoma cells with the luciferase reporter gene vector pGL3 containing full-length constructs of human (h) or mouse (m) ACTH-R promoter together with a DAX-1 expression plasmid. These experiments were also performed using ACTH-R promoter 5'-deletion constructs and constructs mutated at the SF-1-binding sites. RESULTS: We found a negative correlation between DAX-1 and ACTH-R mRNA expression (R=-0.47, P
-
Genetic influence of an ACTH Receptor promoter polymorphism on adrenal androgen secretion
European journal of endocrinology, 2005Co-Authors: Nicole Reisch, Felix Beuschlein, Marc Slawik, Oliver Zwermann, Martin ReinckeAbstract:Objective: Adrenocorticotropic hormone (ACTH) is the primary secretagogue stimulating secretion of adrenal androgens (AA). Yet, genetic and environmental factors are assumed to play a determining role in the regulation of their biosynthesis and thus might explain the high variability of AA levels. Here we investigate the influence of an ACTH Receptor promoter polymorphism affecting ACTH Receptor gene transcription on ACTH-dependent dehydroepiandrosterone (DHEA) secretion. Design: We recently reported a polymorphism within the transcription initiation site of the ACTH Receptor gene promoter that alters the consensus sequence from CTC to CCC at 22bp. This results in lower promoter activity in vitro and is associated with impaired cortisol response to ACTH stimulation in vivo. We now studied 14 normal, lean volunteers aged 20‐35 years (eight CTC/CTC and six CCC/CCC carriers) in a 6-h ACTH stimulation test. Methods: After overnight dexamethasone suppression, ACTH1-24 was administered continuously in each subject with hourly increasing doses (120‐3840ng/m 2 body surface area/h) within a 6-h period. On a separate day, baseline DHEA samples were collected. Results: In the 6-h ACTH stimulation test, CTC/CTC carriers showed a significantly higher DHEA response than CCC/CCC carriers (area under the curve: 19367^2919 vs 11098^1241nmol/l per min; P , 0.04, Mann‐Whitney U-test). In contrast, baseline DHEA concentrations did not differ between groups. Conclusion: These data demonstrate that genetic variations within the ACTH Receptor promoter result in decreased DHEA secretion. Thus, we might have identified one of the genetic factors responsible for variation in ACTH-dependent DHEA secretion. European Journal of Endocrinology 153 711‐715
-
Clinical and molecular evidence for DAX-1 inhibition of steroidogenic factor-1-dependent ACTH Receptor gene expression.
European journal of endocrinology, 2005Co-Authors: Oliver Zwermann, Felix Beuschlein, Albrecht Klink, Enzo Lalli, Paolo Sassone-corsi, Martin ReinckeAbstract:Background: The ACTH Receptor (ACTH-R) is a member of the seven transmembrane domain Receptor super-family. In non-functional adrenal adenomas and adrenocortical carcinomas, ACTH-R expression is low. However, no inhibitory factor for ACTH-R expression has been defined to date. DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1) is a general repressor of steroid production, inhibiting steroidogenic factor-1 (SF-1)-dependent expression of multiple steroidogenic enzymes. The aim of this study was to investigate whether ACTH-R gene transcription is affected by DAX-1 and whether this mechanism is involved in down-regulation of ACTH-R expression in adrenocortical tumors. Methods: We screened 22 adrenocortical tumors for ACTH-R and DAX-1 mRNA expression by Northern blot. For in vitro analyses we co-transfected mouse Y1 adrenocortical carcinoma cells with the luciferase reporter gene vector pGL3 containing full-length constructs of human (h) or mouse (m) ACTH-R promoter together with a DAX-1 expression plasmid. These experiments were also performed using ACTH-R promoter 5 0 -deletion constructs and constructs mutated at the SF-1-binding sites. Results: We found a negative correlation between DAX-1 and ACTH-R mRNA expression (R ¼ 2 0.47, P , 0.02). Accordingly, in vitro expression of DAX-1 significantly reduced hACTH-R and mACTH-R promoter activity by 89 and 55% respectively. DAX-1 inhibition was also present in the shortest construct of a series of 5 0 -deletion constructs of the human promoter extending from 2 64 to þ 40 bp relative to the transcription start site. Mutation of the SF-1-binding sites within the hACTH-R promoter resulted in reduced or abolished DAX-1 inhibition, arguing for a mechanism that involves SF-1 for DAX-1 inhibition. Conclusions: These data support the concept that DAX-1 is a major repressor of ACTH-R gene expression in vitro and in vivo.
-
Characterization of an adrenocorticotropin (ACTH) Receptor promoter polymorphism leading to decreased adrenal responsiveness to ACTH.
The Journal of clinical endocrinology and metabolism, 2004Co-Authors: Marc Slawik, Albrecht Klink, Martin Reincke, Nicole Reisch, Oliver Zwermann, Christiane Maser-gluth, Maik Stahl, Felix BeuschleinAbstract:The ACTH Receptor has a pivotal role in the regulation of adrenal cortisol secretion. Here, we describe a polymorphism within the transcription initiation site of the ACTH Receptor promoter altering the consensus sequence from CTC to CCC. The prevalence of the polymorphism in 1266 unrelated healthy men was 80.2% for CTC/CTC, 19.0% for CTC/CCC, and 0.8% for CCC/CCC, respectively. In vitro studies using luciferase assays demonstrated a lower basal (CCC, 73 ± 4%; CTC, 100 ± 5%; P = 0.02) and forskolin-stimulated (CCC, 143 ± 13%; CTC, 194 ± 15%; P = 0.0008) promoter activity in the CCC construct compared with CTC. The clinical significance of the in vitro findings was investigated by a 6-h ACTH stimulation test with increasing ACTH1–24 doses in normal subjects, demonstrating a blunted cortisol response in CCC/CCC subjects compared with CTC/CTC individuals (area under the curve, 12176 ± 966; 16334 ± 1051 nmol/liter·min; P < 0.03). Accordingly, after CRH stimulation, subjects with CCC/CCC showed a higher ACTH/c...
-
ACTH-Receptor expression, regulation and role in adrenocortial tumor formation
European journal of endocrinology, 2001Co-Authors: Felix Beuschlein, Martin Fassnacht, Albrecht Klink, Bruno Allolio, Martin ReinckeAbstract:The regulation of the ACTH-Receptor gene is unique in that it is up-regulated by its own ligand, ACTH. Ligand-induced up-regulation of ACTH-Receptor expression may be an important adaptive process directed towards optimizing adrenal responsiveness to ACTH in the context of physiological stress and the maintenance of metabolic homeostasis in which the adrenals play a pivotal role. Whereas enhancement by ligand-induced up-regulation permits a more efficient and rapid glucocorticoid response, negative feedback regulation of glucocorticoids in the hypothalamus and pituitary inhibits ACTH secretion and allows a balanced adrenal response to stress. Since the cloning of the promoter region of the ACTH Receptor, considerable progress in the understanding of the regulatory processes has been made. The effects of ACTH on ACTH-Receptor expression is dependent on cAMP, probably mediated through AP-1. The profound effect of three SF-1-binding sites in the ACTH-Receptor promoter was demonstrated by deletion experiments. Conversely, ACTH-Receptor expression can be suppressed by adrenal-specific transcription factors,like DAX-1. Despite an extensive search, no activating ACTH-Receptor mutations have been found in adrenal tumors,excluding the ACTH Receptor as a relevant oncogene in adrenal tumorigenesis. However, the ACTH Receptor may act as a differentiation factor as suggested by LOH in adrenal carcinomas with an undifferentiated tumor type. In benign adrenal tumors, a strong correlation between ACTH-Receptor expression and expression of P450 steroidogenic enzymes is evident. This close regulative relationship is lost in adrenal carcinoma, probably as a result of tumor dedifferentiation. Down-regulation of ACTH-Receptor expression in normal and neoplastic tissue can be achieved by adrenostatic compounds such as aminoglutethimide and metyrapone.
