Androgen Receptor

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Albert O. Brinkmann - One of the best experts on this subject based on the ideXlab platform.

  • The Androgen Receptor in prostate cancer.
    Pathology Research and Practice, 2011
    Co-Authors: Jan Trapman, Albert O. Brinkmann
    Abstract:

    Summary The Androgen Receptor is a member of the family of nuclear Receptors. In its activated form as an Androgen Receptor ligand complex (the ligand can either be testosterone or 5a-dihydrotestosterone), the Androgen Receptor is able to regulate a specific expression of target genes. The Androgen Receptor is expressed at high levels in male reproductive tissues. Mutations in the Androgen Receptor gene are the molecular cause of the Androgen insensitivity syndrome, which is characterized by an aberrant male or an apparently female phenotype. Expansion of a CAG-repeat, encoding a polymorphic glutamine stretch is the cause of a rare motor neuron disease (Kennedy's disease). Hormonal therapy is the treatment of choice for metastatic prostate cancer. Hormone refractory prostate tumors in general still express Androgen Receptor. In a proportion of the late stage prostate tumors, somatic mutations in the Androgen Receptor gene have been described. Mutations can result in diminished ligand specificity of the Androgen Receptor. Furthermore, it has been hypothesized that ligand independent mechanisms can also be involved in Androgen Receptor activation.

  • In situ photolabelling of the human Androgen Receptor.
    Journal of Steroid Biochemistry, 2003
    Co-Authors: Albert O. Brinkmann, J. Bolt-de Vries, George G J M Kuiper, Eppo Mulder
    Abstract:

    In situ photoaffinity labelling of the human Androgen Receptor has been performed in the LNCaP (Lymph Node Carcinoma of the Prostate) cell line. The covalently labelled Receptors were identified by SDS-PAGE. Intact LNCaP cells, incubated with [3H]-R1881 and subsequently irradiated with u.v. light and directly solubilized in SDS-buffer, revealed two photolabelled protein bands at 110 and 50 kDa. Irradiation of intact cells and subsequent isolation of nuclei followed by extraction with 0.5 M NaCl resulted in one major photolabelled protein band at 110 kDa. The labelling of this band could be completely suppressed by a 100-fold molar excess of non-radioactive R1881. Photolabelling of Androgen Receptors in a cytosolic preparation of LNCaP cells after anion exchange chromatography resulted in a much lower labelling efficiency compared with the in situ labelling procedure, although the Androgen Receptor was purified 100-fold. The steroid binding domain of the human Androgen Receptor has been partially mapped with chymotrypsin and S. aureus V8 protease digestion. Proteolytic digestion with chymotrypsin of purified photoaffinity-labelled 110 kDa human Androgen Receptor resulted in the generation of a 15 kDa peptide which still contains the covalently linked hormone. It is concluded that the in situ photoaffinity labelling technique can be applied successfully for characterization of the steroid binding domain of Androgen Receptors in prostate cancer cells and in other Androgen target cells. Furthermore, it was demonstrated that the human Androgen Receptor is a monomer with a molecular mass of 110 kDa, of which the steroid binding site is confined to a 15 kDa domain.

  • Androgen Receptor abnormalities
    The Journal of Steroid Biochemistry and Molecular Biology, 2003
    Co-Authors: Albert O. Brinkmann, George G J M Kuiper, C. Ris-stalpers, H. C. J. Van Rooij, Gabriela Romalo, Mark Trifiro, Eppo Mulder, Leonard Pinsky, H.u. Schweikert, Jan Trapman
    Abstract:

    The human Androgen Receptor is a member of the superfamily of steroid hormone Receptors. Proper functioning of this protein is a prerequisite for normal male sexual differentiation and development. The cloning of the human Androgen Receptor cDNA and the elucidation of the genomic organization of the corresponding gene has enabled us to study Androgen Receptors in subjects with the clinical manifestation of Androgen insensitivity and in a human prostate carcinoma cell line (LNCaP). Using PCR amplification, subcloning and sequencing of exons 2-8, we identified a G----T mutation in the Androgen Receptor gene of a subject with the complete form of Androgen insensitivity, which inactivates the splice donor site at the exon 4/intron 4 boundary. This mutation causes the activation of a cryptic splice donor site in exon 4, which results in the deletion of 41 amino acids from the steroid binding domain. In two other independently arising cases we identified two different nucleotide alterations in codon 686 (GAC; aspartic acid) located in exon 4. One mutation (G----C) results in an aspartic acid----histidine substitution (with negligible Androgen binding), whereas the other mutation (G----A) leads to an aspartic acid----asparagine substitution (normal Androgen binding, but a rapidly dissociating Androgen Receptor complex). Sequence analysis of the Androgen Receptor in human LNCaP-cells (lymph node carcinoma of the prostate) revealed a point mutation (A----G) in codon 868 in exon 8 resulting in the substitution of threonine by alanine. This mutation is the cause of the altered steroid binding specificity of the LNCaP-cell Androgen Receptor. The functional consequences of the observed mutations with respect to protein expression, specific ligand binding and transcriptional activation, were established after transient expression of the mutant Receptors in COS and HeLa cells. These findings illustrate that functional errors in the human Androgen Receptor have an enormous impact on phenotype and fertility.

  • Forskolin-induced dephosphorylation of the Androgen Receptor impairs ligand binding.
    Biochemistry, 1998
    Co-Authors: L J Blok, P E De Ruiter, Albert O. Brinkmann
    Abstract:

    When Androgen Receptor containing cells are cultured in the presence of the PKA stimulator forskolin, a rapid dephosphorylation of the Androgen Receptor occurs resulting in a decrease in the amount of 112 kDa Androgen Receptor isoform and an increase in 110 kDa Androgen Receptor isoform on SDS-PAGE. To establish which amino acid residues in the Androgen Receptor were phosphorylated in control and forskolin-treated cells, trypsin-digested Androgen Receptors were subjected to RP-HPLC analysis and subsequently to Edman degradation. It was observed that serine residues 506, 641, and 653 were potentially phosphorylated in control cells, while after forskolin treatment strong evidence was obtained that phosphorylation of serines 641 and 653 was significantly reduced. When the dephosphorylated Androgen Receptor was analyzed for its transcription activation capacity, it was observed that Androgen-induced transcriptional regulation of two endogenous genes (PSA) and beta 1-subunit of Na,K-ATPase), in cells cultured in the presence of forskolin, was inhibited as compared to the control situation. The observation that the dephosphorylated Androgen Receptor was transcriptionally less active was further strengthened by the finding that the dephosphorylated Androgen Receptor was markedly impaired in ligand binding (Bmax was found to be reduced by approximately 40%). The current investigations show for the first time a clear function for the rapid phosphorylation which occurs directly after synthesis of the Androgen Receptor, namely, effective ligand binding.

  • Androgen Receptor phosphorylation.
    Endocrine Research, 1996
    Co-Authors: L J Blok, P E De Ruiter, Albert O. Brinkmann
    Abstract:

    : Phosphorylation of transcription factors plays an important role in regulation of gene expression. DNA-binding, transactivation activity, and subcellular trafficking of specific transcription factors have been shown to be regulated by phosphorylation/dephosphorylation. Steroid hormone Receptors are phospho-proteins, and mutations in phosphorylation sites significantly affect the transactivation capacity of these ligand-dependent transcription factors. At present, it is unknown which amino acid residues of the human Androgen Receptor are phosphorylated and whether phosphorylation of particular sites is a prerequisite for proper Androgen Receptor function. The aim of our future research is to map all phosphorylation sites in the human Androgen Receptor, and to analyze their importance by mutational analysis in vitro and in vivo using a number of functional assays.

Michael J. Mcphaul - One of the best experts on this subject based on the ideXlab platform.

  • Functional analysis of the human Androgen Receptor promoter.
    Molecular and Cellular Endocrinology, 1996
    Co-Authors: Karen K Takane, Michael J. Mcphaul
    Abstract:

    Although Androgen Receptor levels vary widely during development, our previous studies have suggested that a single promoter is active in a number of human and rat tissues and cell lines. To examine the elements controlling Androgen Receptor expression, we performed deletion mapping and site-directed mutagenesis of the human Androgen Receptor promoter and assayed these promoter fusions in human cell lines that produce the Androgen Receptor as well as those deficient in the Androgen Receptor, both in the presence and absence of Androgen. Our studies identify a region (-74 to +87) surrounding the site of transcription initiation that constitutes the core of the Androgen Receptor promoter. When assayed in T47D cells (an AR-expressing cell line), this segment was sufficient to direct the expression of reporter genes at levels similar to that observed for larger promoter fragments, and further deletions led to an appreciable loss of promoter activity. DNA sequences surrounding this region appear to modulate the activity of this minimal promoter in a cooperative fashion. Site-directed mutagenesis and mobility shift assays demonstrated the importance of regulatory regions upstream of the transcription initiation site including an SP1 binding site and two segments with similarities to consensus HLH protein binding sites (E-boxes). Androgen treatment did not cause a decrease in activity of any of the transiently transfected promoter fusions tested, suggesting that the promoter does not contain the information necessary for autoregulation or that a posttranscriptional or posttranslational mechanism is responsible for the regulation of AR mRNA by ligand. Furthermore, the Androgen Receptor promoter fusions displayed differing transcriptional activities when transfected into two cell lines deficient in Androgen Receptor expression suggesting heterogeneity in the mechanisms responsible for this deficiency.

  • Mutations of the Androgen Receptor coding sequence are infrequent in patients with isolated hypospadias.
    The Journal of Clinical Endocrinology and Metabolism, 1995
    Co-Authors: A Alléra, J D Wilson, M A Herbst, James E. Griffin, Hans U. Schweikert, Michael J. Mcphaul
    Abstract:

    Androgen Receptor defects can cause severe hypospadias. To examine the possibility that Androgen Receptor defects are a common cause of such deficiencies, we have determined the coding sequence of the Androgen Receptor gene in nine patients with severe hypospadias. The analysis of the Androgen Receptor coding sequence predicts a normal amino acid sequence for the Androgen Receptor of eight of the nine patients, indicating that the observed defects in virilization are infrequently caused by mutations of the open-reading frame of the Androgen Receptor. These findings demonstrate the importance of family history and endocrine studies in identifying patients likely to harbor coding sequence mutations in the Androgen Receptor gene, and they serve to focus attention on other genes that may influence Androgen action in this group of patients.

  • The Androgen Receptor of the urogenital tract of the fetal rat is regulated by Androgen
    Molecular and Cellular Endocrinology, 1994
    Co-Authors: Frans M. Bentvelsen, Michael J. Mcphaul, J D Wilson, Fredrick W. George
    Abstract:

    Abstract To provide insight into Androgen-mediated virilization, we measured the Androgen Receptor in tissues of male and female rat fetuses prior to and during the period of phenotypic sex differentiation. Western immunoblotting was performed utilizing an antibody directed against the 21 amino-terminal segment of the Androgen Receptor. In immunoblots prepared from urogenital tract tissues of day 17 male and female fetal rats, this antibody specifically recognizes a 11 OK protein band characteristic of the Androgen Receptor. Androgen Receptor levels were low to undetectable in a variety of non-urogenital tract tissues. After day 18 of fetal development, the amount of Androgen Receptor decreased in female urogenital tissues, and by day 22 the amount of immunoreactive Androgen Receptor was higher in the male urogenital sinus and tubercle than in the corresponding tissues of the female. Administration of 5α-dihydrotestosterone to pregnant rats at a dose of 50 mg/kg body weight per day from day 12 to day 22 caused an increase in immunoreactive Androgen Receptor in the female urogenital sinus and tubercle to levels approaching those in male tissues. Administration of the Androgen antagonist flutamide (100 mg/kg body weight per day) during the same interval caused a reduction in Androgen Receptor level in the urogenital sinus and tubercle of the male. These findings suggest that Androgens modulate the amount of Androgen Receptor in the embryonic urogenital tract either by inducing the proliferation of Androgen-responsive cells or by increasing Androgen Receptor levels in individual cells.

  • Molecular defects in the Androgen Receptor causing Androgen resistance.
    Journal of Investigative Dermatology, 1992
    Co-Authors: Michael J. Mcphaul, Marco Marcelli
    Abstract:

    Patients with Androgen resistance exhibit a spectrum of abnormalities of male sexual development ranging from 46,XY phenotypic women (complete testicular feminization) to undervirilized fertile men. The definition of the Androgen Receptor gene structure has permitted the identification of the defects causing Androgen resistance in a number of patients. In some individuals Androgen resistance is caused by large-scale structural alterations in the Androgen Receptor gene. In most patients, however, the Androgen Receptor mutation is the result of single nucleotide substitutions, which cause premature termination or amino acid replacement that result in the synthesis of defective Androgen Receptor proteins. These amino acid substitutions identify residues crucial to the normal function of the Androgen Receptor protein.

  • decreased levels of the Androgen Receptor in the mature rat phallus are associated with decreased levels of Androgen Receptor messenger ribonucleic acid
    Endocrinology, 1991
    Co-Authors: Karen K Takane, Jean D Wilson, Michael J. Mcphaul
    Abstract:

    Growth of the penis at sexual maturation is under the control of Androgens, but growth ceases as the organ reaches adult size despite continued high levels of circulating Androgen. Previous studies have shown that the cessation of penile growth is associated with a decrease in the quantity of Androgen Receptor, as detected by ligand binding and immunological methods. In the current studies we demonstrate that the decreased Androgen Receptor levels correlate with a decrease in Androgen Receptor mRNA content in the penile corpus and os, but not in the glans penis. These findings suggest that modulation of Androgen Receptor mRNA levels in the body of the penis may be important to the control of Androgen-dependent growth in the tissue, and that the control of Androgen Receptor mRNA levels differs among the different cell types that comprise the penis. To explore the mechanisms controlling Androgen Receptor expression, we examined the transcription initiation site of the rat Androgen Receptor gene in ventral p...

Jan Trapman - One of the best experts on this subject based on the ideXlab platform.

  • The Androgen Receptor in prostate cancer.
    Pathology Research and Practice, 2011
    Co-Authors: Jan Trapman, Albert O. Brinkmann
    Abstract:

    Summary The Androgen Receptor is a member of the family of nuclear Receptors. In its activated form as an Androgen Receptor ligand complex (the ligand can either be testosterone or 5a-dihydrotestosterone), the Androgen Receptor is able to regulate a specific expression of target genes. The Androgen Receptor is expressed at high levels in male reproductive tissues. Mutations in the Androgen Receptor gene are the molecular cause of the Androgen insensitivity syndrome, which is characterized by an aberrant male or an apparently female phenotype. Expansion of a CAG-repeat, encoding a polymorphic glutamine stretch is the cause of a rare motor neuron disease (Kennedy's disease). Hormonal therapy is the treatment of choice for metastatic prostate cancer. Hormone refractory prostate tumors in general still express Androgen Receptor. In a proportion of the late stage prostate tumors, somatic mutations in the Androgen Receptor gene have been described. Mutations can result in diminished ligand specificity of the Androgen Receptor. Furthermore, it has been hypothesized that ligand independent mechanisms can also be involved in Androgen Receptor activation.

  • Evolution of the Androgen Receptor pathway during progression of prostate cancer.
    Cancer Research, 2006
    Co-Authors: Peter J. M. Hendriksen, Jan Trapman, Natasja Dits, Koichi Kokame, Antoine Veldhoven, Wytske M. Van Weerden, Chris H. Bangma, Guido Jenster
    Abstract:

    The present work focused on the potential involvement of selective adaptations of the Androgen Receptor pathway in the initiation and progression of prostate cancer. We defined the Androgen Receptor pathway by selecting 200 genes that were Androgen responsive in prostate cancer cell lines and/or xenografts. This Androgen Receptor pathway gene signature was then used for profiling prostate cancer xenografts and patient-derived samples. Approximately half of the Androgen Receptor pathway genes were up-regulated in well-differentiated prostate cancer compared with normal prostate. Functionally distinct parts of the Androgen Receptor pathway were specifically down-regulated in high-grade cancers. Unexpectedly, metastases have down-regulated the vast majority of Androgen Receptor pathway genes. The significance of this progressive down-regulation of Androgen Receptor pathway genes was shown for a few Androgen Receptor-regulated genes. Lower mRNA expression of HERPUD1, STK39, DHCR24, and SOCS2 in primary prostate tumors was correlated with a higher incidence of metastases after radical prostatectomy. HERPUD1 mRNA expression predicted the occurrence of metastases almost perfectly. In vitro experiments showed that overexpression of the stress response gene HERPUD1 rapidly induces apoptosis. Based on the functions of the genes within the distinct subsets, we propose the following model. Enhanced Androgen Receptor activity is involved in the early stages of prostate cancer. In well-differentiated prostate cancer, the Androgen Receptor activates growth-promoting as well as growth-inhibiting and cell differentiation genes resulting in a low growth rate. The progression from low-grade to high-grade prostate carcinoma and metastases is mediated by a selective down-regulation of the Androgen Receptor target genes that inhibit proliferation, induce differentiation, or mediate apoptosis.

  • Androgen Receptor abnormalities
    The Journal of Steroid Biochemistry and Molecular Biology, 2003
    Co-Authors: Albert O. Brinkmann, George G J M Kuiper, C. Ris-stalpers, H. C. J. Van Rooij, Gabriela Romalo, Mark Trifiro, Eppo Mulder, Leonard Pinsky, H.u. Schweikert, Jan Trapman
    Abstract:

    The human Androgen Receptor is a member of the superfamily of steroid hormone Receptors. Proper functioning of this protein is a prerequisite for normal male sexual differentiation and development. The cloning of the human Androgen Receptor cDNA and the elucidation of the genomic organization of the corresponding gene has enabled us to study Androgen Receptors in subjects with the clinical manifestation of Androgen insensitivity and in a human prostate carcinoma cell line (LNCaP). Using PCR amplification, subcloning and sequencing of exons 2-8, we identified a G----T mutation in the Androgen Receptor gene of a subject with the complete form of Androgen insensitivity, which inactivates the splice donor site at the exon 4/intron 4 boundary. This mutation causes the activation of a cryptic splice donor site in exon 4, which results in the deletion of 41 amino acids from the steroid binding domain. In two other independently arising cases we identified two different nucleotide alterations in codon 686 (GAC; aspartic acid) located in exon 4. One mutation (G----C) results in an aspartic acid----histidine substitution (with negligible Androgen binding), whereas the other mutation (G----A) leads to an aspartic acid----asparagine substitution (normal Androgen binding, but a rapidly dissociating Androgen Receptor complex). Sequence analysis of the Androgen Receptor in human LNCaP-cells (lymph node carcinoma of the prostate) revealed a point mutation (A----G) in codon 868 in exon 8 resulting in the substitution of threonine by alanine. This mutation is the cause of the altered steroid binding specificity of the LNCaP-cell Androgen Receptor. The functional consequences of the observed mutations with respect to protein expression, specific ligand binding and transcriptional activation, were established after transient expression of the mutant Receptors in COS and HeLa cells. These findings illustrate that functional errors in the human Androgen Receptor have an enormous impact on phenotype and fertility.

  • Mechanisms of Androgen Receptor activation and function.
    The Journal of steroid biochemistry and molecular biology, 1999
    Co-Authors: A O Brinkmann, Cor A Berrevoets, L J Blok, P E De Ruiter, P Doesburg, K Steketee, Jan Trapman
    Abstract:

    Androgens play a crucial role in several stages of male development and in the maintenance of the male phenotype. Androgens act in their target cells via an interaction with the Androgen Receptor, resulting in direct regulation of gene expression. The Androgen Receptor is a phosphoprotein and modulation of the phosphorylation status of the Receptor influences ligand-binding and consequently transcription activation of Androgen responsive genes. Androgen binding induces a conformational change in the ligand-binding domain, accompanied by additional Receptor phosphorylation. Subsequently the liganded Androgen Receptor interacts with specific Androgen response elements in the regulatory regions of Androgen target genes, resulting in stimulation of gene expression. Anti-Androgens induce a different conformational change of the ligand-binding domain, which does not or only partially result in stimulation of transactivation. Interestingly, different anti-Androgens can induce different inactive conformations of the Androgen Receptor ligand-binding domain. Recent evidence strongly supports a ligand dependent functional interaction between the ligand-binding domain and the NH2-terminal transactivating domain of the Androgen Receptor. Two regions in the NH2-terminal domain are involved in this interaction, whereas in the ligand-binding domain the AF-2 AD core region is involved.

  • Androgen Receptor mutations
    The Journal of Steroid Biochemistry and Molecular Biology, 1995
    Co-Authors: Albert O. Brinkmann, Guido Jenster, C. Ris-stalpers, J.a.g.m. Van Der Korput, Hennie T. Brüggenwirth, Annemie L.m. Boehmer, Jan Trapman
    Abstract:

    Male sexual differentiation and development proceed under direct control of Androgens. Androgen action is mediated by the intracellular Androgen Receptor, which belongs to the superfamily of ligand-dependent transcription factors. At least three pathological situations are associated with abnormal Androgen Receptor structure and function: Androgen insensitivity syndrome (AIS), spinal and bulbar muscular atrophy (SBMA) and prostate cancer. In the X-linked Androgen insensitivity syndrome, defects in the Androgen Receptor gene have prevented the normal development of both internal and external male structures in 46,XY individuals. Complete or gross deletions of the Androgen Receptor gene have not been found frequently in persons with complete Androgen insensitivity syndrome. Point mutations at several different sites in exons 2–8 encoding the DNA- and Androgen-binding domain, have been reported for partial and complete forms of Androgen insensitivity. A relatively high number of mutations were reported in two different clusters in exon 5 and in exon 7. The number of mutations in exon 1 is extremely low and no mutations have been reported in the hinge region, located between the DNA-binding domain and the ligand-binding domain and which is encoded by the first half of exon 4. Androgen Receptor gene mutations in prostate cancer are very rare and are reported only in exons 4–8. The X-linked spinal and bulbar muscle atrophy (SBMA; Kennedy's disease) is associated with an expanded length (> 40 residues) of one of the polyglutamine stretches in the N-terminal domain of the Androgen Receptor.

Guido Jenster - One of the best experts on this subject based on the ideXlab platform.

  • Evolution of the Androgen Receptor pathway during progression of prostate cancer.
    Cancer Research, 2006
    Co-Authors: Peter J. M. Hendriksen, Jan Trapman, Natasja Dits, Koichi Kokame, Antoine Veldhoven, Wytske M. Van Weerden, Chris H. Bangma, Guido Jenster
    Abstract:

    The present work focused on the potential involvement of selective adaptations of the Androgen Receptor pathway in the initiation and progression of prostate cancer. We defined the Androgen Receptor pathway by selecting 200 genes that were Androgen responsive in prostate cancer cell lines and/or xenografts. This Androgen Receptor pathway gene signature was then used for profiling prostate cancer xenografts and patient-derived samples. Approximately half of the Androgen Receptor pathway genes were up-regulated in well-differentiated prostate cancer compared with normal prostate. Functionally distinct parts of the Androgen Receptor pathway were specifically down-regulated in high-grade cancers. Unexpectedly, metastases have down-regulated the vast majority of Androgen Receptor pathway genes. The significance of this progressive down-regulation of Androgen Receptor pathway genes was shown for a few Androgen Receptor-regulated genes. Lower mRNA expression of HERPUD1, STK39, DHCR24, and SOCS2 in primary prostate tumors was correlated with a higher incidence of metastases after radical prostatectomy. HERPUD1 mRNA expression predicted the occurrence of metastases almost perfectly. In vitro experiments showed that overexpression of the stress response gene HERPUD1 rapidly induces apoptosis. Based on the functions of the genes within the distinct subsets, we propose the following model. Enhanced Androgen Receptor activity is involved in the early stages of prostate cancer. In well-differentiated prostate cancer, the Androgen Receptor activates growth-promoting as well as growth-inhibiting and cell differentiation genes resulting in a low growth rate. The progression from low-grade to high-grade prostate carcinoma and metastases is mediated by a selective down-regulation of the Androgen Receptor target genes that inhibit proliferation, induce differentiation, or mediate apoptosis.

  • Glycogen Synthase Kinase-3β Is Involved in the Phosphorylation and Suppression of Androgen Receptor Activity
    Journal of Biological Chemistry, 2004
    Co-Authors: Thomas R. Salas, Anita L. Sabichi, Shao Yong Chen, Lirim Shemshedini, Funda Vakar-lopez, Patricia Troncoso, Guido Jenster, Akira Kikuchi, Milind Suraokar
    Abstract:

    Abstract Kinases can phosphorylate and regulate Androgen Receptor activity during prostate cancer progression. In particular, we showed that glycogen synthase kinase-3β phosphorylates the Androgen Receptor, thereby inhibiting Androgen Receptor-driven transcription. Conversely, the glycogen synthase kinase-3β inhibitor lithium chloride suppressed the glycogen synthase kinase-3β-mediated phosphorylation of the Androgen Receptor, thereby enabling Androgen Receptor-driven transcription to occur. The Androgen Receptor hinge and ligand-binding domains were important for both the phosphorylation and the inhibition of transcriptional activity of the Receptor by glycogen synthase kinase-3β. Furthermore, Androgen Receptor phosphorylation was augmented by LY294002, an indirect inhibitor of protein kinase B/Akt that inhibits glycogen synthase kinase-3β. We also showed that the mutation of various phosphorylation sites on glycogen synthase kinase-3β affected the ability of these mutants to co-distribute with the Androgen Receptor in the cell nucleus, also that both glycogen synthase kinase-3β and Androgen Receptor proteins can be found in cell nuclei of prostate cancer tissue samples. Because glycogen synthase kinase-3β activity is suppressed after the enzyme is phosphorylated by protein kinase B/Akt and Akt activity frequently increases during the progression of prostate cancer, nullification of the glycogen synthase kinase-3β-mediated suppression of Androgen Receptor activity by Akt likely contributes to prostate cancer progression.

  • Androgen Receptor mutations
    The Journal of Steroid Biochemistry and Molecular Biology, 1995
    Co-Authors: Albert O. Brinkmann, Guido Jenster, C. Ris-stalpers, J.a.g.m. Van Der Korput, Hennie T. Brüggenwirth, Annemie L.m. Boehmer, Jan Trapman
    Abstract:

    Male sexual differentiation and development proceed under direct control of Androgens. Androgen action is mediated by the intracellular Androgen Receptor, which belongs to the superfamily of ligand-dependent transcription factors. At least three pathological situations are associated with abnormal Androgen Receptor structure and function: Androgen insensitivity syndrome (AIS), spinal and bulbar muscular atrophy (SBMA) and prostate cancer. In the X-linked Androgen insensitivity syndrome, defects in the Androgen Receptor gene have prevented the normal development of both internal and external male structures in 46,XY individuals. Complete or gross deletions of the Androgen Receptor gene have not been found frequently in persons with complete Androgen insensitivity syndrome. Point mutations at several different sites in exons 2–8 encoding the DNA- and Androgen-binding domain, have been reported for partial and complete forms of Androgen insensitivity. A relatively high number of mutations were reported in two different clusters in exon 5 and in exon 7. The number of mutations in exon 1 is extremely low and no mutations have been reported in the hinge region, located between the DNA-binding domain and the ligand-binding domain and which is encoded by the first half of exon 4. Androgen Receptor gene mutations in prostate cancer are very rare and are reported only in exons 4–8. The X-linked spinal and bulbar muscle atrophy (SBMA; Kennedy's disease) is associated with an expanded length (> 40 residues) of one of the polyglutamine stretches in the N-terminal domain of the Androgen Receptor.

  • Nuclear import of the human Androgen Receptor
    Biochemical Journal, 1993
    Co-Authors: Guido Jenster, Jan Trapman, Albert O. Brinkmann
    Abstract:

    Nuclear import of the human Androgen Receptor was investigated by immunocytochemical analysis of Androgen Receptor deletion and substitution mutants, which were transiently expressed in COS-1 cells. The signal responsible for nuclear import is encoded by amino-acid residues 608-625 and is functionally similar to the bipartite nucleoplasmin nuclear-localization signal. Although the subcellular distribution of Androgen Receptors mutated in the DNA-binding domain was unchanged compared with the wild-type Androgen Receptor, in the presence of ligand these mutations resulted in part of the Receptor population forming clusters. Depending on the presence or absence of the bipartite nuclear localization signal, clusters were formed in the nucleus or in the cytoplasm, respectively. Expression of the wild-type Androgen Receptor in different cell lines revealed a cell-line-specific subcellular distribution of the unliganded Receptor. The Androgen Receptor was predominantly nuclear when expressed in HeLa cells, whereas mainly cytoplasmic staining was observed when it was expressed in COS-1 cells. In the presence of hormone, the Androgen Receptor was located in the nucleus, independent of the cell line that was expressing the Receptor. Anti-Androgens and various steroid hormones induced the nuclear localization of the wild-type Androgen Receptor in a dose-dependent way, without activating transcription of an Androgen-regulated reporter gene. This indicates that the inability of the tested compounds to activate transcription is not due to inhibited nuclear import.

Karen K Takane - One of the best experts on this subject based on the ideXlab platform.

  • Functional analysis of the human Androgen Receptor promoter.
    Molecular and Cellular Endocrinology, 1996
    Co-Authors: Karen K Takane, Michael J. Mcphaul
    Abstract:

    Although Androgen Receptor levels vary widely during development, our previous studies have suggested that a single promoter is active in a number of human and rat tissues and cell lines. To examine the elements controlling Androgen Receptor expression, we performed deletion mapping and site-directed mutagenesis of the human Androgen Receptor promoter and assayed these promoter fusions in human cell lines that produce the Androgen Receptor as well as those deficient in the Androgen Receptor, both in the presence and absence of Androgen. Our studies identify a region (-74 to +87) surrounding the site of transcription initiation that constitutes the core of the Androgen Receptor promoter. When assayed in T47D cells (an AR-expressing cell line), this segment was sufficient to direct the expression of reporter genes at levels similar to that observed for larger promoter fragments, and further deletions led to an appreciable loss of promoter activity. DNA sequences surrounding this region appear to modulate the activity of this minimal promoter in a cooperative fashion. Site-directed mutagenesis and mobility shift assays demonstrated the importance of regulatory regions upstream of the transcription initiation site including an SP1 binding site and two segments with similarities to consensus HLH protein binding sites (E-boxes). Androgen treatment did not cause a decrease in activity of any of the transiently transfected promoter fusions tested, suggesting that the promoter does not contain the information necessary for autoregulation or that a posttranscriptional or posttranslational mechanism is responsible for the regulation of AR mRNA by ligand. Furthermore, the Androgen Receptor promoter fusions displayed differing transcriptional activities when transfected into two cell lines deficient in Androgen Receptor expression suggesting heterogeneity in the mechanisms responsible for this deficiency.

  • decreased levels of the Androgen Receptor in the mature rat phallus are associated with decreased levels of Androgen Receptor messenger ribonucleic acid
    Endocrinology, 1991
    Co-Authors: Karen K Takane, Jean D Wilson, Michael J. Mcphaul
    Abstract:

    Growth of the penis at sexual maturation is under the control of Androgens, but growth ceases as the organ reaches adult size despite continued high levels of circulating Androgen. Previous studies have shown that the cessation of penile growth is associated with a decrease in the quantity of Androgen Receptor, as detected by ligand binding and immunological methods. In the current studies we demonstrate that the decreased Androgen Receptor levels correlate with a decrease in Androgen Receptor mRNA content in the penile corpus and os, but not in the glans penis. These findings suggest that modulation of Androgen Receptor mRNA levels in the body of the penis may be important to the control of Androgen-dependent growth in the tissue, and that the control of Androgen Receptor mRNA levels differs among the different cell types that comprise the penis. To explore the mechanisms controlling Androgen Receptor expression, we examined the transcription initiation site of the rat Androgen Receptor gene in ventral p...

  • Androgen Receptor Levels in the Rat Penis Are Controlled Differently in Distinctive Cell Types
    Endocrinology, 1991
    Co-Authors: Karen K Takane, Douglas A. Husmann, Michael J. Mcphaul, Jean D Wilson
    Abstract:

    The rat phallus grows during sexual maturation as serum Androgen concentrations rise to adult levels, and growth ceases when sexual maturity is attained despite the continued presence of adult serum Androgen levels. This cessation of growth is correlated temporally with a diminution in the levels of Androgen Receptor, as detected by assays of ligand binding. To determine whether the change in Androgen Receptor content occurs in all cells in the tissue, immunohistochemical studies of the penile Androgen Receptor were performed in rats of different ages. In immature animals and animals castrated prepubertally, the Androgen Receptor is detected in virtually all cell types, including the corpus cavernosum penis, the small lateral cavernous bodies, the corpus cavernosum urethra, skin, urethra, and os penis. By contrast, in the mature rat penis minimal Androgen Receptor is evident within the corporal tissues and os, although immunoreactivity remains detectable in the penile skin and urethra. It is concluded tha...