Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the binding of dihydrotestosterone-receptor complexes (DHT-R) from human genital skin fibroblasts to oligodeoxyribonucleotides and DNA. Following incubation of fibroblasts with 2 nM [3H]DHT (45 min, 37 degrees C), DHT-R were prepared as total fibroblast sonicates (sonication of cells in 0.5 M KCl), intact fibroblast cytosol (100000 X g supernatant) or intact fibroblast nuclear extract (sonication of nuclei in 0.5 M KCl). DHT-R were also prepared by incubation of fractionated fibroblast cytosol with 4 nM [3H]DHT (4 h, 0 degrees C). Optimal conditions were established for binding of DHT-R from total fibroblast sonicates to oligo-dT cellulose: 60 min, 0 degrees C, low salt (0.05-0.10 M KCl), linearity with DHT-R concentration, and nucleotide saturation. With total fibroblast sonicates the rank order of DHT-R binding was oligo-dT approximately equal to -dG greater than DNA greater than -dC greater than or equal to -dA approximately equal to -dI. Intact fibroblast cytosol displayed a similar preference of DHT-R binding to oligo-dT and -dG but the binding was quantitatively higher than for total fibroblast sonicates, the binding for fractionated fibroblast cytosolic DHT-R formed at 0 degrees C being quantitatively lower. However, binding of DHT-R from cytosol (0 degrees C) to DNA-cellulose was equal to that for DHT-R from cytosol (37 degrees C). Binding of DHT-R from intact fibroblast nuclear extracts was lower than for total fibroblast sonicates. Preparations from cells of patients with receptor-negative, complete androgen insensitivity lacked both DHT-R formation and specific oligonucleotide binding. Binding of oligonucleotides to DHT-R from cells of patients with receptor-positive, complete androgen insensitivity could not be distinguished from that of normal cells. These results suggest: (a) androgen receptor-steroid complexes recognize and bind to certain preferred deoxyribonucleotides; (b) various factors affect the quantitative binding of DHT-R from different cellular preparations to deoxyribonucleotides; and (c) neither qualitative nor quantitative abnormalities for DHT-R of complete androgen-insensitive patients were detectable from oligonucleotide or DNA binding.
Mol Cell Endocrinol 1983 Oct
PMID:Human androgen insensitivity mutation does not alter oligonucleotide recognition by the androgen receptor-DHT complex. 664 73

Estrogen receptors are present in cytosol prepared from the accessory sex organs (vesicular gland, proprostate, prostate, bulbourethral gland) of sexually immature and of sexually mature rabbits. The receptor in these organs from animals of both age groups has a sedimentation coefficient of 8-10S on low ionic strength (0.01 M KCl) sucrose gradients. Under high ionic strength (0.4 M KCl) conditions, the receptor sediments at approximately 4S. The cytoplasmic estrogen receptor from the epididymis shows age-dependent changes in its sedimentation coefficient. It is 8S under low ionic strength conditions when prepared from immature rabbits and 4S under identical conditions when prepared from sexually mature animals. Although the dissociation constant of the cytoplasmic estrogen receptor in the immature and mature epididymis and accessory sex organs remains constant during development (approximately 0.1 nM), the number of available cytoplasmic estrogen binding sites declines from about 160 fmoles/mg cytosol protein in the immature rabbit to about 40 fmoles/mg cytosol protein in the adult animal. The estrogen receptor in the accessory sex organs is highly specific, the relative affinities of various potential competitors being: estradiol and estrone = 1, diethylstilbestrol = 0.3, estriol = 0.2, tamoxifen = 0.08, testosterone = 0.0004 and 5 alpha-DHT = 0.00005. Changes with age in the physicochemical characteristics of the estrogen receptor and in the concentration of binding sites suggest that the estrogen receptor may be involved in the development and physiological regulation of the male reproductive tract.
Mol Cell Endocrinol 1983 Dec
PMID:Identification of cytoplasmic estrogen receptors in the accessory sex organs of the rabbit and their comparison to the cytoplasmic estrogen receptor in the epididymis. 665 71

Androgen-binding protein (ABP) is present in the guinea-pig testis, epididymis and epididymal fluid. Guinea-pig ABP sediments as an approx. 4.6S species on sucrose gradients containing 0.01 M KCl. Electrophoresis on non-denaturing polyacrylamide gels indicated that specific androgen binding was present in epididymal cytosol, but not in plasma. Time-course studies indicated that binding equilibrium is approached in about 2.5 h; the dissociation half-time of [3H]5 alpha-DHT from guinea-pig ABP is 5.64 +/- 0.62 h (n = 6) at 4 degrees C. The relative affinities of some steroids for guinea-pig ABP in relation to 5 alpha-DHT = 1 are: testosterone = 0.55 +/- 0.13 (n = 4), estradiol = 0.14 +/- 0.03 (n = 4), the anti-androgen cyproterone acetate = 0.0025 +/- 0.0002 (n = 3). Guinea-pig ABP exhibited an equilibrium dissociation constant of 6.34 +/- 0.52 nM (n = 3) at 4 degrees C and there were 3.43 +/- 0.78 (n = 3) pmoles of binding sites per mg of protein when homogenates of the whole epididymis were assayed. The concentration of ABP was lowest in the caput-corpus region of the epididymis, highest in the proximal cauda, and intermediate in the distal cauda. Essentially all of the ABP present in the distal cauda was intraluminal, as evidenced by the fact that flushing of the duct eliminated most of the [3H]5 alpha-DHT binding activity.
Mol Cell Endocrinol
PMID:The presence of androgen-binding protein in the guinea-pig testis, epididymis and epididymal fluid. 689 45

Partially-purified 5 alpha-dihydrotestosterone-receptor (DHT-R) complexes, extracted from normal genital skin fibrolasts (GSF) previously labelled with [3H]DHT, dissociate with monophasic kinetics and dissociation rate constants (k-2) of 10, 6, 3 and 2 x 10(-3) min-1 at 40, 37, 32 and 29 degrees C, respectively. An Arrhenius plot yields an activation energy of 28 kcal/mole. We studied 2 subjects who have constitutional androgen insensitivity (AI) despite a normal level of specific DHT-R activity in their GSF. Subject 1 has complete AI and unambiguous female external genitalia; subject 2 has partial AI and had ambiguous external genitalia at birth. In contrast to normal, the DHT-R complexes extracted from the GSF of these 2 subjects dissociate with biphasic kinetics. At 37 degrees C the k-1 of their early ('fast') component is 21 +/- 0.4(+/-SEM) x 10(-3) min-1(n = 7), while that of their late ('slow') component (k-2) is 7.8 +/- 0.3 x 10(-3) min-1 (n = 7). The latter value is very similar to the single k-2 (6.1 +/- 0.1 x 10(-3) min-1, n = 9) of the DHT-R complexes extracted from normal fibroblasts. When dissociation of DHT-R complexes is studied with intact fibroblasts, monophasic kinetics are observed for both the normal and mutant subjects. A k-1 of 18 x 10(-3) min-1 was previously observed for both mutant subjects at 37 degrees C (normal: K-2, 5.9 +/- 0.3 x 10(-3) min-1, n = 15). At 40 degrees C subject 1 has a rate constant of 25 while that of subject 2 is 50 x 10(-3) min-1(normal: 10 x 10(-3) min-1). An Arrhenius plot of the results from subject 1 yields an activation energy of 18 kcal/mole. The 2 sets of data suggest that inability of DHT-R complexes to transform from a rapidly dissociating to a slowly-dissociating form within intact target cells is a marker of genetic mutations that alter the androgen receptor and thereby cause certain types of partial of complete AI.
Mol Cell Endocrinol 1982 Feb
PMID:Defective activation of androgen-receptor complexes: a marker of androgen insensitivity. 705 33

In the presence of sodium thiocyanate (NaCNS), partially purified 5 alpha-dihydrotestosterone-receptor (DHT-R) complexes extracted from normal genital skin fibroblasts (GSF) dissociate with complex (biphasic) kinetics. The rate constant of the 'fast' component and the magnitude of the 'slow' component vary with temperature (29-37 degrees C) and NaCNS concentration (0.1-0.4 M). Equimolar sodium bromide is much less effective; potassium chloride up to 1 M has no effect. DHT-R complexes from the GSF of a subject with partial androgen insensitivity (PAI) yield biphasic dissociation profiles that differ from normal and are influenced by NaCNS. Together with the temperature-dependent, first-order (monophasic) dissociative behavior of normal DHT-R complexes in the absence of NaCNS (Kaufman et al., 1982), the foregoing data have been used to construct a kinetic model involving the dissociation of DHT from 3 conformationally related forms of the androgen-receptor complex: (1) dysactivated; (2) preactivated; (3) activated.
Mol Cell Endocrinol 1982 Jul
PMID:Sodium thiocyanate: a probe for the conformations of the androgen-receptor complex. 711 88

The entire androgen metabolism of the human prostate is an integral part of the DHT mediated cellular processes, which eventually give rise to the androgen responsiveness of the prostate. Therefore, the potential activities of various androgen metabolizing enzymes were studied. Moreover, the impact of aging on the androgen metabolism and the inhibition of 5 alpha-reductase by finasteride were studied. In epithelium (E) and stroma (S) of normal (NPR) and hyperplastic human prostate (BPH), for each enzyme being involved in the conversion either of testosterone via DHT, 3 alpha- and 3 beta-diol to the C19O3-triols or from testosterone to androstenedione and vice versa, the amount (Vmax) and Michaelis constant (Km) were determined by Lineweaver-Burk plots. Furthermore, Vmax/Km quotients were calculated, which served as an index for the potential enzyme activity. 17 enzymes showed a mean Vmax/Km > or = 0.10. The top four were the 5 alpha-reductases in E and S of NPR and BPH. Among those, the highest activity was found in E of NPR (1.6 +/- 0.2). Moreover, in E a significant age-dependent decrease of 5 alpha-reductase activity occurred, whereas in stroma rather constant activities were found over the whole age range. Similar age-dependent alterations were found for the cellular DHT levels. Finally, the finasteride inhibition of 5 alpha-reductase (IC50;nM) was stronger in E (35 +/- 17) than in S (126 +/- 15). In conclusion, 5 alpha-reductase is: (a) the outstanding androgen metabolizing enzyme in NPR and BPH; (b) dictating the DHT enrichment in the prostate; (c) under the impact of aging; and (d) preferentially inhibited by finasteride in E.
J Steroid Biochem Mol Biol 1995 Jun
PMID:Potential activities of androgen metabolizing enzymes in human prostate. 754 2

The crucial role played by androgens in the growth of prostatic carcinoma is now well established. However, the mechanisms of this proliferative action are still poorly understood. Experiments have been performed to clarify: (1) the metabolism of androgens in prostatic tumor cells; and (2) the role played by locally produced growth factors in the autocrine regulation of prostatic tumor cell proliferation and the possible regulation exerted by testosterone (T) on the activity of these factors. These studies have been performed by utilizing the human androgen-responsive prostatic cancer LNCaP cell line. (1) By incubating LNCaP cells with different 14C-labeled androgenic precursors, it has been shown that all the major key enzymes involved in the metabolism of androgens (5 alpha-reductase, 17 beta-hydroxysteroid-oxidoreductase, 3 alpha- and 3 beta-hydroxysteroid-oxidoreductases) are present and active in these cells. In particular, the 5 alpha-reductase, which converts T and delta 4 to DHT and 5 alpha-A respectively, seems to be more active when delta 4 is the substrate, suggesting a preference for this precursor. (2) The hypothesis that LNCaP cells might produce LHRH (or a LHRH-like peptide) has been verified by RT-PCR, performed in the presence of a pair of specific oligonucleotide primers. A cDNA band of the expected size (228 bp), which specifically hybridized with a 32P-labeled LHRH oligonucleotide probe, has been obtained in LNCaP cells. To clarify the possible role played by this factor in the regulation of tumor growth, LNCaP cells, cultured in steroid-free conditions, have been treated with a LHRH antagonist; the treatment resulted in a significant increase of cell proliferation. Taken together, these data indicate that a LHRH (or LHRH-like) growth modulatory system is expressed in LNCaP cells and plays an inhibitory role in the regulation of tumor cell proliferation. This system seems to be regulated in a negative way by steroids. Growth factors endowed with stimulatory activity, such as EGF and TGF alpha, have also been shown to be produced by LNCaP cells. The present studies show that the immunoprecipitation of the EGF receptor with a specific monoclonal antibody (Ab225) reveals a protein band of the expected size (170 kDa) which is phosphorylated even in basal conditions. Moreover, the treatment of LNCaP cells, cultured in serum-free conditions, either with a monoclonal antibody against the EGF receptor, or with immunoneutralizing antibodies against EGF and TGF alpha, results in a significant decrease of cell proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)
J Steroid Biochem Mol Biol 1995 Jun
PMID:Growth of the androgen-dependent tumor of the prostate: role of androgens and of locally expressed growth modulatory factors. 762 87

In plasma, most steroid hormones are bound and transported by the specific binding protein, testosterone-estradiol-binding globulin (TeBG). For years, it was believed that the only function of this protein was to regulate the concentration of free steroids in plasma. However, a number of reports have provided evidence for the presence of specific TeBG receptors on plasma membranes. Furthermore, the interaction of TeBG with its receptor was shown to be inhibited when steroids are bound to TeBG, suggesting that TeBG is an allosteric protein. The purpose of this manuscript is to review the evidence that androgen-binding proteins bind to membrane receptors, and, in some cells, this binding stimulates cAMP accumulation, and transfer TeBG/ABP into tissue as a consequence of receptor mediated endocytosis. Recent studies from our laboratories have demonstrated binding and uptake of TeBG by MCF-7 breast cancer cells. The interaction of unligated rabbit TeBG with membranes from MCF-7 cells resulted in a time and concentration-dependent increase in adenylate cyclase activity. The TeBG alone also had a reproducible effect on intact cells by increasing cAMP accumulation by 30-35%. The addition of DHT to cells, after TeBG has been allowed to bind, resulted in increases in cAMP of greater than 4-fold. This effect was not blocked by antiandrogens. These data support the hypothesis that extracellular SHBG is a regulator of cellular function through a membrane receptor that is coupled to adenylate cyclase.
J Steroid Biochem Mol Biol 1995 Jun
PMID:Receptors for androgen-binding proteins: internalization and intracellular signalling. 762 10

Reevaluating the assay for rat steroid 5 alpha-reductase isozymes in prostate and epididymis homogenates we encountered an extreme pH-dependency of the type II isozyme. The time-course of the metabolism of testosterone (T) to 17 beta-hydroxy-5 alpha-androstan-3-one (DHT) at acidic pH shows an initial burst when the homogenate is not brought to pH before the start of the incubation. Therefore, the rat type II 5 alpha-reductase isozyme does not follow Michaelian law under these conditions making a single time point measurement invalid. Assessing the pH-optimum of 5 alpha-reduction in both rat prostate and epididymis homogenates we found a strong substrate dependency: at high substrate concentrations a pH-optimum for the type II isozyme of pH 5.0 was found, whereas at lower concentrations pH 5.5 is optimal. Establishing Vmax (maximum velocities) and Km (affinity constants) for the 5 alpha-reduction of T at pH 4.5-8.0, the efficiency optimum Vmax/Km appeared to be pH 5.5 in both prostate and epididymis homogenates. Specifically at acidic pH these kinetic characteristics of the type II isozyme vary many-fold. Discrepancies in literature concerning 5 alpha-reductase characteristics can, at least in part, be attributed to the choice of optimal pH, or to pH shifts during the assay.
J Steroid Biochem Mol Biol 1995 Aug
PMID:Rat steroid 5 alpha-reductase kinetic characteristics: extreme pH-dependency of the type II isozyme in prostate and epididymis homogenates. 766 92

Androgens oppose the actions of estrogen on a number of neuroendocrine functions in the rat including prolactin and gonadotropin secretion and the activation of the female pattern of sex behavior. Although in nonneural tissues antiestrogenic actions of androgens have been related to actions at the level of the estrogen receptor, previous attempts to demonstrate effects of nonaromatizable androgens on estrogen receptor levels in the brain have been unsuccessful, possibly because of the poor anatomical resolution of the methods used. We have used a new in vitro autoradiographic assay combined with an 125I-labeled estrogen receptor ligand to test the hypothesis that the nonaromatizable androgen, 5 alpha-dihydrotestosterone (5 alpha-DHT), may act to reduce estrogen binding in specific regions of the brain involved in reproductive neuroendocrine and behavioral responses. This in vitro autoradiographic method allows selective measurement of occupied estrogen receptors in tissue sections. Gonadectomized/adrenalectomized rats were divided into two groups per sex. All animals received daily injections of estradiol benzoate (EB: 40 micrograms/kg body wt) for 4 days. Animals in the 5 alpha-DHT treatment group received 5 alpha-DHT (10 mg/kg body wt) every 12 h for 4 days, while animals in the control group received vehicle injections. Animals were killed 4 h after the final EB/5 alpha-DHT injection and their brains processed for in vitro autoradiography. As previously reported, higher levels of estrogen binding were observed in the ventrolateral aspect of the ventromedial nucleus (vIVMN) and the periventricular and medial preoptic area of the female compared to the male.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Neurosci 1994 Dec
PMID:Androgen treatment decreases estrogen receptor binding in the ventromedial nucleus of the rat brain: a quantitative in vitro autoradiographic analysis. 770 28


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