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Androgen-binding proteins in rat epididymis: properties of a cytoplasmic receptor for androgen similar to the androgen receptor in ventral prostate and different from androgen-binding protein (ABP).

The cytoplasmic recptor (CR) in rat epididymal 105,000 g supernatant was separated from the androgen-binding protein (ABP) by gel electrophoresis following labeling with [1,2,6,7-3H]-testosterone in vivo. ABP disappeared from epididymal supernatants after castration of hypophysectomy, while CR remained unchanged. CR was evenly distributed between caput and cauda, while much more ABP was present in caput. Properties of CR in epididymis and prostate were similar and distinctly different from ABP. Binding to CR was destroyed by charcoal treatment (1 mg/mg protein) of supernatant for 0 degrees C for 6 h, heating at 50 degrees C for 30 min, or exposure to the sulfhydryl blocking reagent, p-chloromercuriphenylsulfonate (1mM) at 25 degrees C for 30 min, while binding to ABP was unaffected. The isoelectric pH of CR (5.8) was higher than that of ABP (4.6). Dissociation of radioactive 5alpha-dihydrotestosterone (DHT) from CR and nuclear receptors was extremely slow (half-time at 0 degrees C is greater than 2 days), while dissociation from ABP was rapid (half-time at 0 degrees C is similar to 6 min). Cyproterone acetate (250 mg/100 g body weight) inhibited binding to CR both in epididymis and ventral prostate but did not affect binding to ABP. Nuclear uptake was inhibited by cyproterone to the same extent as binding to CR, indicating that nuclear uptake and binding are dependent on CR and independent of ABP. The time-course of uptake and binding in epididymal supernatant and nuclear fractions was essentially the same 1 day after bilateral castration when both CR and ABP were present or 8 days after castration when CR alone was present. It is concluded that the cytoplasmic receptor for androgen in rat epididymis has properties very similar to the androgen receptor in ventral prostate but different from ABP.

Androstenedione

Androgen-induced biochemical responses in epithelium lacking androgen receptors: characterization of androgen receptors in the mesenchymal derivative of urogenital sinus.

Heterotypic tissue recombinants, composed of adult bladder epithelium obtained from testicular feminization syndrome mice (TfmBLE) and embryonic wild-type rat urogenital sinus mesenchyme (UGM) were grown as subcapsular renal grafts in male athymic nude mice for 30 days. The resultant prostatic tissue that developed was subjected to extensive biochemical analyses for androgen receptors. From previous autoradiographic studies it was shown that UGM possesses androgen receptors and induces the TfmBLE to form prostatic ductal-acinar epithelium that lacks androgen receptors. The purpose of the present study is to biochemically characterize the mesenchymal androgen receptors. According to results obtained by autoradiographic analyses, androgen receptors are expressed in the mesenchyme of tissue recombinants. Cytosolic androgen receptors analyzed by the Scatchard method utilizing R-1881 as a ligand showed that the dissociation constant (Kd) of androgen receptors localized within the mesenchyme of the tissue recombinants differs from that found in the mouse prostate gland, but resembles that found in the rat ventral prostate (VP). Sucrose density gradient analysis of the cytosol androgen receptors showed the presence of 8 S [3H]dihydrotestosterone (DHT) binding component under the low salt condition. The mesenchymal androgen receptors are capable of translocating efficiently from cytosol to nuclear compartment, seemingly unaffected by adjacent TfmBLE. The quantity of both cytosol and nuclear androgen receptors expressed in tissue recombinants is only about 1/3 of that found in the rat VP and is in agreement with the morphometric analysis of tissue recombinants, which indicated that about 1/3 of the cells in the tissue recombinants are stromal cells. These results extend previous autoradiographic results and further suggest that androgen receptors present in the mesenchymal compartment may be necessary for the expression of androgen-elicited responses in the TfmBLE that lacks androgen receptors. In addition, this study confirms a novel model system for the study of mesenchymal androgen receptors in tissues unmolested by mechanical or enzymatic dissociation.

Androgen-Insensitivity Syndrome

Androgen receptors in the anterior pituitary and central nervous system of the androgen "insensitive" (Tfm) rat: correlation between receptor binding and effects of androgens on gonadotropin secretion.

The cytosol fractions of the anterior pituitary, hypothalamus, preoptic area and brain cortex of androgen "insensitive" (Tfm) rats possess androgen receptors. However, in the Tfm rats the androgen binding per mg protein was only 10-15% of that in the corresponding normal littermates (Nl). The physicochemical properties of the androgen receptors in the anterior pituitary of the Tfm rat were indistinguishable from those of the normal rat. Thus, no distinctive differences were observed with regard to electrophoretic mobility in 3.25% polyacrylamide gels, isoelectric point (pI=5.8), binding affinity (KD=1.5 X 10(-9)M), temperature stability, sulfhydryl dependence and steroid specificity. It is, therefore, likely that the very low androgen binding capacity by the anterior pituitary and the central nervous system is due to an extreme reduction in the receptor number rather than to the presence of abnormal receptors. Since in the Tfm animals the androgen receptor number is reduced by 85-90%, it is to be expected that very high doses of androgens would be required to achieve hormonal effects. In fact, low doses of 5alpha-dihydrotestosterone propionate (50 mug/100 g body weight) given sc daily for 12 days had no effect on serum levels of LH and FSH. However, very high doses (2 mg/100 g body weight) of testosterone propionate and 5alpha-dihydrotestosterone propionate, which maintained circulating androgen levels above 20 ng/ml, significantly reduced serum gonadotropin levels in castrated Tfm rats. In normal littermates both low and high doses of the androgens suppressed gonadotropin secretion to low levels. These findings strongly indicate that androgen receptors are essential to androgen action on the anterior pituitary and central nervous system in the rat. The serum levels of testosterone (7.7+/-0.15 (SE) ng/ml) and 5alpha-dihydrotestosterone (0.37+/-0.06 ng/ml) were significantly higher in intact Tfm rats than in normal littermates (2.6+/-0.03 and less than 0.1 ng/ml, respectively). The failure of the elevated concentrations of serum androgens to reduce the high serum levels of LH and FSH in intact Tfm rats is most likely due to the extreme reduction of the androgen receptor number and the consequent insufficient hypothalamic and/or pituitary response to androgens.

Adrenal Glands

Complete androgen insensitivity due to deletion of exon C of the androgen receptor gene highlights the functional importance of the second zinc finger of the androgen receptor in vivo.

Androgen-dependent gene transcription is mediated by the androgen receptor (AR) through interaction of its central zinc finger region with specific DNA sequences on target genes. Failure of this receptor-mediated gene transcription results in end organ resistance to androgens-the androgen insensitivity syndromes. In a pair of siblings with complete androgen insensitivity who had supranormal levels of androgen binding in genital skin fibroblasts, polymerase chain reaction and Southern blot analysis of the androgen receptor gene confirmed by polymerase chain reaction and sequence analysis of AR cDNA, revealed an in-frame deletion of exon C encoding the second zinc finger of the receptor. The mutant receptor in cultured genital skin fibroblasts had normal androgen binding affinity and was localized in the nucleus but had markedly reduced DNA-binding affinity. When recreated in vitro and tested in a cotransfection assay system the mutant receptor failed to activate transcription of an androgen-responsive reporter gene. This naturally occurring mutation highlights the functional dependence of the AR upon its second zinc finger in vivo and explains the complete insensitivity to androgen manifest by the affected individuals despite increased androgen binding. The elevated AR levels in the subjects' genital skin fibroblasts further suggests a possible role for the second zinc finger in autoregulation of receptor levels in vivo.

Androgen-Insensitivity Syndrome

Loss of androgen dependency with preservation of functional androgen receptors in androgen-dependent mouse tumor (Shionogi Carcinoma 115).

Shionogi Carcinoma 115 (SC 115) is an androgen-dependent mouse tumor. Chiba Subline 2 (CS 2) is an androgen-independent subline derived from SC 115. CS 2 contains androgen receptors (AR), but is refractory to androgen and does not exhibit androgen-related responses which are observed in SC 115. In the present study the structure and function of AR in SC 115 and CS 2 are examined using cloned cells. There were no gross rearrangements or deletions in the AR genes of these cell lines when compared by Southern blot analysis with the AR gene in the mouse seminal vesicle. SC 115 and CS 2 expressed AR mRNA of normal size. When the cDNA containing DNA- and androgen-binding domains of the AR genes of both cell lines were amplified by polymerase chain reaction, no mutations were found in these regions. SC 115 and CS 2 were transfected with a plasmid containing a long terminal repeat of mouse mammary tumor virus linked to the chloramphenicol acetyltransferase (CAT) gene. Androgen stimulation of these transfectants resulted in equal elevation of CAT activity. These results indicated that the androgen-independent CS 2 contained functionally normal AR which were identical to those in the androgen-dependent parent tumor.

Androgens

Androgen receptor, testosterone uptake and karyotype in androgen-dependent mouse tumor (SC 115) and its androgen-independent subline (CS 2).

Content of androgen receptor, retention of injected testosterone and karyotype of SC 115, androgen-dependent tumor, were compared with those of CS 2, an androgen-independent subline derived from SC 115. Although Bmax was less than that of SC 115, androgen receptor was present in the cytosol and the nuclear extract from CS 2. To examine the ability for androgen retention, a large amount of testosterone was injected into tumor-bearing mice, and the amount of androgen in the crude nuclear and postnuclear fractions of tumors was compared. In both fractions, retention of injected androgen was higher in the SC 115 than in the CS 2. Since most of the injected testosterone was not metabolized in the tissues and the injection of testosterone 5 alpha-reductase inhibitor showed no significant influence on the growth rate of the SC 115, intracellular active androgen was assumed to be testosterone in these tumor cells. As the CS 2 was tetraploid, the androgen independency of the CS 2 seems to be related to chromosomal changes.

Animals

Androgen resistance associated with a qualitative abnormality of the androgen receptor and responsive to high dose androgen therapy.

A 46,XY infant with perineoscrotal hypospadias and microphallus was identified in a family in which seven individuals have severe hypospadias that is inherited in a pattern compatible with an X-linked defect. The infant had small testes that were palpable in the labioscrotal folds, the proximal urethra was male in character, and there was no vagina. Serum testosterone rose from 0.5 to 5.1 nmol/L in response to hCG, and there was a negligible clinical response to a short term course of testosterone enanthate. A clinical diagnosis of male pseudohermaphroditism due to androgen resistance was made. Studies in cultured genital skin fibroblasts disclosed normal 5 alpha-reductase activity, a normal amount of high affinity dihydrotestosterone binding, and normal up-regulation of androgen receptors when monolayers were incubated with dihydrotestosterone or mibolerone. Fibroblast cytosol preparations contained a normal 7-8S sedimenting peak of androgen binding. However, androgen binding in monolayers decreased 60% when the assay temperature was raised from 30 to 41 C, and the dissociation rate of ligand from the receptor was enhanced 5-fold compared to the control value, establishing the diagnosis of androgen resistance due to a qualitative abnormality of the androgen receptor. Because of parental decision to raise the patient as a male, he was given two courses of high dose testosterone cypionate when he was 2.5 and 3.5 yr old (100 mg every 2 weeks for six doses). This treatment produced significant phallic growth, making it possible to undertake surgical correction of the hypospadias. We postulate that the impairment of androgen receptor function was overcome in part by the large dose of androgen.

Chorionic Gonadotropin

Androgen receptor defects in patients with minimal and partial androgen resistance classified according to a model of androgen-receptor complex energy states.

We have characterized intracellularly the androgen-receptor (A-R) complexes formed by genital skin fibroblasts from 2 unrelated males with qualitative defects of the androgen receptor: one has a small nonhypospadic penis as part of a syndrome of mild androgen resistance; the other was born with ambiguous external genitalia. The dissociation rate constants of testosterone, methyltrienolone (MT), dihydrotestosterone (DHT) and mibolerone (MB) from normal androgen receptors were determined at various temperatures: when plotted by the method of Arrhenius, they yielded a linear hierarchy of dissociation states with energies of state IV greater than III greater than II greater than I, respectively. Relative to this hierarchy, patient A-R complexes were displaced to higher, androgen-inappropriate energies in a mutant-distinctive pattern. MB- or MT-R complexes of both patients were thermolabile; however, both up-regulated normally in response to prolonged incubation with either hormone. Apparent equilibrium affinity constants (Kd) of the DHT- and MB-R complexes formed by both patients were normal; however, the binding capacity (Bmax) for MB in 1 case was subnormal. The distinctive biochemical phenotypes of A-R complexes in these 2 patients with androgen resistance will facilitate the definition of structure-function relations in the androgen receptor, a classical DNA-binding, transcription-regulating protein.

Adolescent

Definition of the human androgen receptor gene structure permits the identification of mutations that cause androgen resistance: premature termination of the receptor protein at amino acid residue 588 causes complete androgen resistance.

We have isolated and characterized the gene encoding the human androgen receptor. The coding sequence is divided into eight coding exons and spans a minimum of 54 kilobases. The positions of the exon boundaries are highly conserved when compared to the location of the exon boundaries of the chicken progesterone and human estrogen receptor genes. Definition of the intron/exon boundaries has permitted the synthesis of specific oligonucleotides for use in the amplification of segments of the androgen receptor gene from samples of total genomic DNA. This technique allows the analysis of all segments of the androgen receptor gene except a small region of exon 1 that encodes the glycine homopolymeric segment. Using these methods we have analyzed samples of DNA prepared from a patient with complete androgen resistance and have detected a single nucleotide substitution at nucleotide 1924 in exon 3 of the androgen receptor gene that results in the conversion of a lysine codon into a premature termination codon at amino acid position 588. The introduction of a termination codon into the sequence of the normal androgen receptor cDNA at this position leads to a decrease in the amount of mRNA encoding the human androgen receptor and the synthesis of a truncated receptor protein that is unable to bind ligand and is unable to activate the long terminal repeat of the mouse mammary tumor virus in cotransfection assays.

Amino Acid Sequence

Androgen levels and androgenization in sex-reversed (XXSxr pseudomale) mouse: absence of initial segment of epididymis is independent of androgens.

The XXSxr pseudomale ("sex-reversed") mouse has an apparently normal male phenotype. This is in accordance with Jost's Principle that, in an animal with androgen-producing testes, phenotype will be fully masculinized, irrespective of chromosomal sex. However, the epididymis of this mutant lacks the Initial Segment. Several alternative explanations were proposed. In the present study we examined the primary of these, viz, androgen insufficiency. We studied androgen levels in serum and tissues of the mutant, and we investigated whether injection of exogenous androgens could induce normal development. The XXSxr pseudomale is not deficient in androgens, nor do exogenous additional androgens induce development of the Initial Segment. It would appear that the abnormal genotype acts on the organ phenotype without intervention of androgens.

Androgens

Mechanism of androgen action: recent observations on the domain structure of androgen receptors and the induction of EGF-receptors by androgens in prostate tumor cells.

In this paper two different aspects of androgen action are reviewed. Polyacrylamide gel electrophoresis of androgen receptors, photoaffinity labeled with R1881 showed that receptors isolated from both human prostate cells and calf uterine cytosol cells are proteins with a molecular mass of approx 110 kD. Purification to homogeneity of this form of the receptor from calf uterus also yielded a 110 kD protein. A molecular model for the DNA-binding form of the receptor is presented in which one polypeptide comprises three active domains: one for ligand binding, one for interaction with nuclear acceptor sites, and a third domain which modulates nuclear interaction. Mild digestion with chymotrypsin or a protease from rat prostates removes the modulating domain and leaves the ligand binding and nuclear interaction domain intact. Trypsin treatment yields a fragment of lower molecular mass containing the ligand binding domain with some affinity for RNA, but not DNA. In vitro studies with a human prostate tumor cell line (LNCaP), suggest that androgens not only directly effect cell growth, but also act indirectly. Both epidermal growth factor (EGF) and androgens stimulate cell growth. In addition androgens stimulate synthesis of receptors for EGF. Thus androgens effect tumor cell growth by autocrine or paracrine mechanisms by making the cells more sensitive for growth factor mediated stimuli.

Androgens

Anti-androgen TSAA-291. V. Effects of the anti-androgen TSAA-291 on the androgen-receptor complex formation from [3H]testosterone in rat ventral prostates.

Intramuscular administration of a new steroidal anti-androgen, TSAA-291 (16 beta-ethyl-17 beta-hydroxy-4-oestren-3-one), in doses of 0.05, 0.5 and 5 mg/kg body weight reduced the in vivo uptake of [3H]testosterone by the ventral prostate of castrated rats of 78, 59 and 37% of the control level, respectively. Analysis on subcellular fractions of the prostate by gel-filtration and sucrose density-gradient centrifugation followed by thin layer chromatographic identification of testosterone metabolites revealed that 5 alpha-dihydrotestosterone (5 alpha-DHT) which was found to be largely bound to macromolecules in the cytosol and nucleus was the predominant metabolite even in the presence of the anti-androgen, and radioactivities corresponding to the 5 alpha-DHT-macromolecular complexes were decreased by the anti-androgen. TSAA-291 also inhibited the in vitro formation of the 5 alpha-DHT-macromolecular complexes in both cytosol and nucleus from minced prostates incubated with [3H]testosterone. The importance of the findings is discussed in connection with the mode of anti-androgenic action of TSAA-291 in terms of the interaction with the androgen receptor.

Androgen Antagonists

Development of androgen-independent spindle cell tumors from androgen-dependent medullary Shionogi carcinoma 115 in androgen-depleted nude mice.

When Shionogi carcinoma 115 (SC115, undifferentiated medullary carcinoma showing compact cell pattern and containing androgen receptor) was transplanted into male and female DS mice, it grew only in males. In contrast to this strict androgen dependency in DS hosts, tumors composed of spindle-shaped cells appeared in more than 80% of cases when SC115 tumor was inoculated into female or castrated male nude athymic (BALB/c-nu/nu) recipients. These spindle cell tumors neither contained cytosol androgen receptor nor showed biologically defined androgen dependency. As spindle cell tumors could be serially transplanted in DS mice but not in BALB/c-+/+ mice and as the original SC115 (medullary carcinoma showing a compact cell pattern) tumor and the spindle cell tumor had many identical chromosome abnormalities, these two types of tumors seem to have a common origin in spite of their morphological, biochemical, and biological differences. Since spindle cells could not be detected histologically in SC115 tumors maintained in intact male DS mice, the present results seem to suggest that SC115 cells may change their morphological, biochemical, and biological characteristics within one passage in androgen-depleted nude athymic mice.

Androgens

Molecular basis of androgen resistance in a family with a qualitative abnormality of the androgen receptor and responsive to high-dose androgen therapy.

We have examined the nature of the mutant androgen receptor in a family with a severe defect in virilization associated with a qualitative defect in receptor function. The androgen receptor gene in this family contains two structural alterations: a single nucleotide substitution at position 2444 in exon 5 (adenosine----guanosine) that converts tyrosine 761 to a cysteine residue and a shortened glutamine homopolymeric segment in exon 1 that encodes 12 rather than the usual 20-22 glutamines. A family study was performed using polymerase chain reaction amplification of the glutamine-rich segment, and it was shown that the sister of the proband does not carry the mutant allele. The effects of these two mutations on the function of the androgen receptor were studied by introducing the changes, individually and in combination, into cDNAs encoding the normal human androgen receptor and analyzing the receptor protein produced after transfection of the cDNAs into eukaryotic cells. The presence of a cysteine residue at position 761 causes rapid dissociation of dihydrotestosterone from the receptor protein. Marked thermolability of the transfected receptor protein, however, was demonstrable only upon introduction of an androgen receptor cDNA containing both the partial deletion of the glutamine homopolymeric segment and a cysteine residue at position 761. Likewise, the ability of the receptor to stimulate a reporter gene is strikingly diminished only when both alterations are present, suggesting that the shortened glutamine homopolymeric segment amplifies the impairment of receptor function caused by the tyrosine to cysteine substitution.

Base Sequence

Effect of androgen on ornithine decarboxylase activity in androgen-dependent mouse mammary tumor (Shionogi Carcinoma 115) and its androgen-independent subline (CS 2).

The activity of ornithine decarboxylase in androgen-dependent mouse mammary tumor (Shionogi Carcinoma 115) was reduced to 25% by castration of tumor-bearing mice and restored to the normal level 12 h after administration of testosterone or 5 alpha-dihydrotestosterone. Administration of estradiol-17 beta to the tumor-bearing castrated mice also stimulated the enzyme activity while progesterone and cortisol had little effect. On the other hand, the enzyme activity was affected by neither castration nor androgen injection to CS 2, which is a subline of SC 115 and completely independent of androgen for growth. The inhibition of ornithine decarboxylase activity in SC 115 by injecting alpha-difluoromethylornithine did not affect the enhancement of RNA polymerase I activity by androgen, showing independent elevation of the levels of the two enzymes by androgen.

Androgens

Androgen binding in the testis: in vitro production of androgen binding protein (ABP) by Sertoli cell cultures and measurement of nuclear bound androgen by a nuclear exchange assay.

Androgen binding activity in the testis has two components. One component, ABP, has been shown to be produced by Sertoli cell cultures for at least 9 days in the absence of exogenously added hormones. FSH (10-100 microgram/ml) markedly enhances the secretion of ABP. MIX has a potentiating effect after long treatment intervals (7 days). In order to study the second component, intracellular androgen receptor, a nuclear exchange assay was developed. Competition for exchange activity using 3H-dihydrotestosterone was significant for a 500 fold excess of testosterone, dihydrotestosteron, progesterone, and cyproterone acetate. The exchange activity was increased 2-10 fold by prior treatment in vitro or in vivo with testosterone. Significant exchange activity was found in long-term hypophysectomized adult and immature animals and in tubule and germ cell fractions. In isolated germ cell fractions, the highest concentration of exchange activity was associated with the most mature elements. These data suggest that androgen exchange activity may exist in both Sertoli cell and germ cell fractions and suggest that the mechanism of action of androgens in the testis is quite complex.

Age Factors

Molecular cloning of androgen receptors from divergent species with a polymerase chain reaction technique: complete cDNA sequence of the mouse androgen receptor and isolation of androgen receptor cDNA probes from dog, guinea pig and clawed frog.

We have cloned and sequenced 2.8 kilobases of cDNA encoding the mouse androgen receptor by RNA amplification with transcript sequencing. Sequence analysis predicts that this cDNA contains an open reading frame of 2697 nucleotides encoding a polypeptide of 899 amino acids. Androgen receptor cDNA probes of dog, guinea pig, and frog were also isolated and sequenced using consensus primers derived from human and rat androgen receptor cDNAs. Northern blot analysis with the species-specific probes revealed similarities in size between amphibian and mammalian mRNAs. These results demonstrate the utility of this technique in obtaining nucleic acid probes and sequence information of steroid receptors from different species. The sequence data and the Northern blot analysis of the receptors in different species demonstrate that the androgen receptor has been well-conserved during evolution.

Amino Acid Sequence

Roles of prepubertal androgen, estrogen or androgen plus prolactin on androgen-induced proliferative response of seminal vesicles in adult mice.

Male mice castrated on day 0 after birth were pretreated daily with testosterone propionate (TP, 4 micrograms/g body weight), 17 beta-estradiol (E2, 0.2 micrograms/g body weight) or vehicle for 21 days starting from day 20. In another experiment, male mice were castrated on day 25; two pituitaries from 60-day-old females were immediately grafted under the capsule of the left kidney in one group. The castrated mice with or without grafts were pretreated daily with TP (4 or 20 micrograms/g body weight) for 36 days starting from day 25, and the left kidney was removed on day 60. Daily TP injections (4 micrograms/g body weight) were started again at 30 days after the end of pretreatments to examine androgen-induced proliferation, and incorporation of 5-[125I]iodo-2'-deoxyuridine into the whole seminal vesicles was used as an index of proliferation. In the neonatally castrated mice, both TP and E2 pretreatments given during the prepubertal period significantly increased seminal vesicle weight even long after the end of the pretreatments. However, androgen-induced proliferative response found in the neonatally castrated adult mice (poor response; long duration with a low peak) was changed to that found in mice castrated at adulthood (good response; short duration with a high peak) by the TP pretreatment only but not at all by the E2 pretreatment. In the mice castrated on day 25, a pharmacological dose of TP or TP plus hyperprolactin could not enhance or change the adult castration type of androgen-induced proliferation induced by physiological prepubertal androgens, although both treatments significantly enhanced the prepubertal growth of the seminal vesicles.

Animals