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V Luu-The

Publications and source records attributed to V Luu-The.

At least 19 recordsLinked to original sources
PubMed2001

Developmental regulation of connexin 43 expression in fetal mouse testicular cells.

Multiple connexins have been identified in testicular cells. Several lines of evidences indicate that, among them, connexin 43 (Cx43) may be unique for control of gonad development and spermatogenesis. To date, however, it is not known whether Cx43 is expressed in the fetal testis and what possible types of cellular interactions mediated by this connexin are critical to male fertility. In the present work, expression of Cx43 was investigated at various developmental ages in cryosections from mouse testis by using specific antibodies against Cx43. In serial or double-labeled sections, Cx43 localization was compared with immunocytochemical distribution of steroidogenic enzyme, 3beta-hydroxysteroid dehydrogenase (3betaHSD), Mullerian inhibitory hormone (MIH), and germinal nuclear cell antigen (GCNA1), which are specific markers, respectively, of interstitial Leydig, Sertoli, and germinal cells. Sections were analyzed by fluorescence microscopy. We found that Cx43 immunofluorescence (IF) was uniformly distributed in the undifferentiated gonad at 11.5 days post coitus (dpc) and in cells of the mesonephric tubules. In the undifferentiated gonad, Cx43 was localized between primordial germ cells and somatic cells. At 12.5 dpc, when the gonad has undergone sexual differentiation, in the interstitium Cx43 was localized in Leydig cells and in the seminiferous cord it was localized between adjacent Sertoli cells. In Leydig and Sertoli cells, Cx43 labeling increased at 14.5, 16.5, and 18.5 dpc. From day 12.5 up to 18.5 dpc, Cx43 was also localized in cell borders between germinal and Sertoli cells. In conclusion, this study demonstrates that from the earliest stages of gonadal development, Cx43 is expressed in the principal cell types that participate in the control of male fertility. It also shows that Cx43 expression in Leydig and Sertoli cells increase during fetal life. Finally, it provides evidence that, throughout embryonic life, Cx43 forms gap junctions between Sertoli and germinal cells.

Animals↗
PubMed2001

Crystallization and preliminary crystallographic results of apo and complex forms of human dehydroepiandrosterone sulfotransferase.

Dehydroepiandrosterone sulfotransferase converts dehydroepiandrosterone (DHEA) and some other steroids to their sulfonated forms. The human enzyme has been crystallized in the presence of substrate (DHEA) alone, in the presence of substrate and non-sulfated cofactor analogue (PAP) and in the absence of both substrate and PAP in our laboratory, with data sets collected at a synchrotron source. The crystals of the uncomplexed form belong to the orthorhombic space group C222(1), with unit-cell parameters a = 85.26, b = 87.69, c = 108.20 A and data 99.2% complete to 2.35 A resolution. The DHEA complex crystallizes in the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 74.46, b = 127.49, c = 44.59 A and data 92.9% complete to 2.15 A resolution. The ternary complex crystallizes in the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 62.25, b = 87.28, c = 138.86 A and data 98.6% complete to 2.50 A resolution. Preliminary molecular-replacement solutions indicate significant variations in dimer formation.

Apoenzymes↗
PubMed2001

Immunohistochemical localization of 3 beta-hydroxysteroid dehydrogenase and 5 alpha-reductase in the brain of the African lungfish Protopterus annectens.

The localization of the enzymes responsible for the biosynthesis of neurosteroids in the brain of dipnoans has not yet been determined. In the present study, we investigated the immunohistochemical distribution of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and 5 alpha-reductase (5 alpha-R) in the brain and pituitary of the African lungfish Protopterus annectens by using antibodies raised against type I human 3 beta-HSD and type I human 5 alpha-R. The 3 beta-HSD and 5 alpha-R immunoreactivities were detected in cell bodies and fibers located in the same areas of the lungfish brain, namely, in the pallium, thalamus, hypothalamus, tectum, and periaqueductal gray. Identification of astrocytes, oligodendrocytes, and neurons with antisera against glial fibrillary acidic protein, galactocerebroside and neurofilaments revealed that, in the lungfish brain, 3 beta-HSD immunolabeling is expressed exclusively by neurons, whereas the 5 alpha-R-immunoreactive material is contained in both neurons and glial cells. In the pituitary gland, 3 beta-HSD- and 5 alpha-R-like immunoreactivity was localized in both the pars distalis and the pars intermedia. The present study provides the first immunocytochemical mapping of two key steroidogenic enzymes in the brain and pituitary of a lungfish. These data strongly suggest that neurosteroid biosynthesis occurs in the brain of fishes, as previously shown for amphibians, birds, and mammals.

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

Gene structure, chromosomal localization and analysis of 3-ketosteroid reductase activity of the human 3(alpha-->beta)-hydroxysteroid epimerase.

Following our previous characterization of the first human 3(alpha-->beta)hydroxysteroid epimerase (hHSE), we determined the genomic structure and chromosomal localization of the hHSE gene using fluorescent in situ hybridization (FISH) in this study. The gene spans 23 kb and contains five exons and four introns. FISH mapping assigned this gene to chromosome band 12q13. Primer extension analysis allowed the identification of a single transcription start site at 179 bp upstream from the ATG start codon. The 5'-flanking sequence lacks a typical TATA box in the proximal region of the transcription start site. However, analysis of the 2 kb promoter region revealed the presence of multiple potential transcription factor binding sites. Furthermore, we studied the 3-ketosteroid reductase activity demonstrated by hHSE in intact cells stably expressing the enzyme. It has been known that, in vitro, 3beta-hydroxysteroid dehydrogenase (3beta-HSD) shows both oxidative and reductive activity. Our results showed that hHSE catalyzes the reduction of 3-ketosteroids to form 3beta-hydroxysteroids while 3beta-HSD cannot catalyze this reaction in intact cells. However, hHSE showed 3-keto reductase activity in both microsomal fractions and intact cells. Since intact cells constitute a system which closely reflects in vivo intracellular conditions, we propose that hHSE might contribute to the cellular 3-ketosteroid reductase activity in the peripheral tissues.

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

Structure of the human 3alpha-hydroxysteroid dehydrogenase type 3 in complex with testosterone and NADP at 1.25-A resolution.

The first crystallographic structure of human type 3 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD3, AKR1C2), an enzyme playing a critical role in steroid hormone metabolism, has been determined in complex with testosterone and NADP at 1.25-A resolution. The enzyme's 17beta-HSD activity was studied in comparison with its 3alpha-HSD activity. The enzyme catalyzes the inactivation of dihydrotestosterone into 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) as well as the transformation of androstenedione into testosterone. Using our homogeneous and highly active enzyme preparation, we have obtained 150-fold higher 3alpha-HSD specificity as compared with the former reports in the literature. Although the rat and the human 3alpha-HSDs share 81% sequence homology, our structure reveals significantly different geometries of the active sites. Substitution of the Ser(222) by a histidine in the human enzyme may compel the steroid to adopt a different binding to that previously described for the rat (Bennett, M. J., Albert, R. H., Jez, J. M., Ma, H., Penning, T. M., and Lewis, M. (1997) Structure 5, 799-T812). Furthermore, we showed that the affinity for the cofactor is higher in the human 3alpha-HSD3 than the rat enzyme due to the presence of additional hydrogen bonds on the adenine moiety and that the cofactor is present under its reduced form in the active site in our preparation.

17-Hydroxysteroid Dehydrogenases↗
PubMed2001

Characterization of the oxidative 3alpha-hydroxysteroid dehydrogenase activity of human recombinant 11-cis-retinol dehydrogenase.

11-cis-Retinol dehydrogenase catalyzes the oxidation of cis-retinols, a rate-limiting step in the biosynthesis of 9-cis-retinoic acid. It is also active toward 3alpha-hydroxysteroids, and thus might be involved in steroid metabolism. To better understand the role of this enzyme, we produced stable transfectants expressing 11-cis-retinol dehydrogenase in human embryonic kidney 293 cells. In vitro enzymatic assays have demonstrated that, with an appropriate exogenous cofactor, the enzyme catalyzes the interconversion of 5alpha-androstane-3alpha,17beta-diol and dihydrotestosterone and that of androsterone and androstanedione. However, using intact transfected cells, we found that the enzyme catalyzes reactions only in the oxidative direction. Thus, it is possible that 5alpha-androstane-3alpha,17beta-diol (an inactive androgen) can be converted into dihydrotestosterone, the most potent androgen, by the action of 11-cis-retinol dehydrogenase. This reaction could constitute a non-classical pathway of production of active androgens in the peripheral tissues. We also showed that all-trans-, 9-cis- and 13-cis-retinol inhibit the oxidative 3alpha-hydroxysteroid steroid activity of 11-cis-retinol dehydrogenase with similar K(i) values. Since all-trans-retinol is a precursor of cis-retinols, its inhibitory effect on the activity suggests that it could play an important role in modulating the formation of 9-cis-retinoic acid. In addition, we examined the effect of several known enzyme modulators, namely carbenoxolone, phenylarsine oxide and phosphatidylcholine, on 11-cis-retinol dehydrogenase activity. Taken together, our results suggest that, in humans, this enzyme might play a role in the biosynthesis of both 9-cis-retinoic acid and dihydrotestosterone.

20-Hydroxysteroid Dehydrogenases↗
PubMed2001

Type 5 17beta-hydroxysteroid dehydrogenase: its role in the formation of androgens in women.

Type 5 17beta-HSD, one of the seven types of 17beta-hydroxysteroid dehydrogenase (17beta-HSD) so far characterized in humans, catalyzes the transformation of 4-androstenedione (4-dione) into testosterone (T). This reaction is also catalyzed by type 3 17beta-HSD which is responsible for pseudohermaphroditism in deficient man but is asymptomatic in deficient women. Since type 3 17beta-HSD is not found in the ovary, whereas type 5 is, it is suggested that the latter is involved in the conversion of 4-androstenedione to testosterone in the ovary. The comparison of type 5 17beta-HSD of different species shows that the human enzyme shares 95 and 78% identity with the monkey and mouse enzymes respectively. In addition, the human and monkey enzymes are labile and are destroyed upon homogenization of the transfected cells, whereas the mouse enzyme is not. Human type 5 17beta-HSD also possesses a high 20alpha-HSD activity that inactivates progesterone, whereas the monkey and mouse enzymes do not have such high 20alpha-HSD activity. Since the endocrine ovary is composed of two types of cells, one producing androgens (theca cells) and the other producing progesterone and estrogens (granulosa cells), it is tempting to suggest that the role of the high 20alpha-HSD activity of type 5 17beta-HSD is to protect the theca cells against the progesterone produced by the granulosa cells. The double activity of type 5 17beta-HSD in the female reproductive tissues is probably necessary to the control of the optimal level of progesterone and sex steroids.

17-Hydroxysteroid Dehydrogenases↗
PubMed2001

Inhibitors of type II 17beta-hydroxysteroid dehydrogenase.

The 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) are involved in the last step of the biosynthesis of sex steroids from cholesterol. This family of steroidogenic enzymes constitutes an interesting target in the control of the concentration of estrogens and androgens. Among the isoforms of 17beta-HSD, type II preferentially catalyzes the oxidation of estradiol (E(2)), testosterone (T), dihydrotestosterone (DHT), and 20alpha-dihydroprogesterone (20alpha-DHP). Based on structure-activity relationship studies, we have developed steroidal spirolactones as inhibitors of type II 17beta-HSD using different steroid nuclei: a C18-steroid (lactones 1 and 10), an antiestrogenic nucleus (lactone 2), and a C19-steroid (lactone 28). We know these inhibitors are selective for type II 17beta-HSD as no or only weak inhibition was observed for types I and III. They also have no proliferative (androgenic) activity on androgen sensitive (AR(+)) Shionogi cells whereas their proliferative (estrogenic) activity on estrogen sensitive (ER(+)) ZR-75-1 cells depends on the nature of the steroid nucleus. Lactones 1 and 10 are weak estrogens, while lactones 2 and 28 do not exert estrogenic activity, in fact lactone 2 is an antiestrogen. Lactones 1, 2, 10 and 28 were also tested in an identical assay with a series of enzyme substrates, C19-steroid diols, and known inhibitors, for the oxidation of testosterone and estradiol into androstenedione and estrone, respectively. From this comparative study, the best inhibitors of type II 17beta-HSD (oxidase activity) were identified, but none of them were clearly more potent than the hydroxylated (reduced) forms of enzyme substrates, E2, T, and DHT. Such inhibitors remain, however, useful tools to, (1) further elucidate the role of type II 17beta-HSD, and (2) regulate the level of active estrogens, androgens and progesterone.

17-Hydroxysteroid Dehydrogenases↗
PubMed2001

DHEA and its transformation into androgens and estrogens in peripheral target tissues: intracrinology.

A new understanding of the endocrinology of menopause is that women, at menopause, are not only lacking estrogens resulting from cessation of ovarian activity but have also been progressively deprived for a few years of androgens and some estrogens originating from adrenal DHEA and androstenedione (4-dione). In fact, serum DHEA decreases by about 60% between the maximal levels seen at 30 years of age to the age of menopause. This decreased secretion of DHEA and DHEA-S by the adrenals is responsible for a parallel decrease in androgen and estrogen formation in peripheral tissues by the steroidogenic enzymes specifically expressed in each cell type in individual target tissues. This new field of endocrinology, called intracrinology, describes the local synthesis of androgens and estrogens made locally in each cell of each peripheral tissue from the adrenal precursors DHEA and 4-dione. These androgens and estrogens exert their action in the same cells where their synthesis takes place and they are released from these target cells only after being inactivated. To further understand the effect of DHEA in women, DHEA has been administered in postmenopausal women for 12 months. Such treatment resulted in increased bone formation and higher bone mineral density accompanied by elevated levels of osteocalcin, a marker of bone formation. Vaginal maturation was stimulated, while no effect was observed on the endometrium. Preclinical studies, on the other hand, have shown that, due to its predominant conversion into androgens, DHEA prevents the development and inhibits the growth of dimethylbenz(a)anthracene-induced mammary carcinoma in the rat, a model of breast cancer. DHEA also inhibits the growth of human breast cancer ZR-75-1 xenografts in nude mice. The inhibitory effect of DHEA on breast cancer is due to an androgenic effect of testosterone and dihydrotestosterone made locally from DHEA. When used as replacement therapy, DHEA is free of the potential risk of breast and uterine cancer, while it stimulates bone formation and vaginal maturation and decreases insulin resistance. The combination of DHEA with a fourth generation SERM, such as EM-652 (SCH 57068), a compound having pure and potent antiestrogenic activity in the mammary gland and endometrium, could provide major benefits for women at menopause (inhibition of bone loss and serum cholesterol levels) with the associated major advantages of preventing breast and uterine cancer. A widely used application of intracrinology is the treatment of prostate cancer where the testicles are blocked by an LHRH agonist while the androgens made locally in the prostate from DHEA are blocked by a pure antiandrogen. Such treatment, called combined androgen blockade, has led to the first demonstration of a prolongation of life in prostate cancer.

Adult↗
PubMed2001

Anatomical and biochemical evidence for the synthesis of unconjugated and sulfated neurosteroids in amphibians.

Various studies have shown that, in mammals, neurons and glial cells are capable of synthesizing bioactive steroids, or neurosteroids, which regulate the activity of the central nervous system (CNS). However, although steroid hormones are involved in the regulation of behavioral and neuroendocrine processes in amphibians, neurosteroid biosynthesis has never been studied in the CNS of non-mammalian vertebrates. Reviewed here are several data sets concerning the production of unconjugated and sulfated neurosteroids in amphibians. These data were obtained by investigating the immunohistochemical localization and activity of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 17beta-hydroxysteroid dehydrogenase (17beta-HSD) and hydroxysteroid sulfotransferase (HST), in the frog brain. Numerous 3beta-HSD-immunoreactive neurons were detected in the anterior preoptic area, nucleus of the periventricular organ, posterior tuberculum, ventral and dorsal hypothalamic nuclei. 17beta-HSD-like immunoreactivity was found in ependymal gliocytes bordering the lateral ventricles of the telencephalon. Two populations of HST-immunoreactive neurons were localized in the anterior preoptic area and the dorsal magnocellular nucleus of the hypothalamus. High amounts of progesterone (PROG), 17-hydroxyprogesterone (17OH-PROG), testosterone (T) and dehydroepiandrosterone sulfate (DHEAS) were measured in the frog brain by combining HPLC analysis of tissue extracts with radioimmunoassay detection. Incubation of telencephalic or hypothalamic explants with tritiated pregnenolone ([3H]PREG) yielded the synthesis of various metabolites including PROG, 17OH-PROG, DHEA and T. Incorporation of [35S]3'-phosphoadenosine 5'-phosphosulfate ([35S]PAPS) and [3H]PREG or [3H]DHEA into frog brain homogenates led to the formation of [3H,35S]pregnenolone sulfate ([3H,35S]PREGS) or [3H,35S]DHEAS, respectively. Altogether, these results demonstrate that the process of neurosteroid biosynthesis occurs in amphibians as previously seen in mammals.

17-Hydroxysteroid Dehydrogenases↗
PubMed2001

High metabolization of catecholestrogens by type 1 estrogen sulfotransferase (hEST1).

Recently, two types of estrogen sulfotransferase, chronologically named types 1 and 2 estrogen sulfotransferase (hEST1 and hEST2), have been described. Since hEST2 selectively catalyzes the sulfonation of ethinyl estradiol as well as that of estrone (E1) and estradiol (E2), but poorly the sulfonation of catecholestrogens, we wanted to assess the ability of hEST1 to metabolize these compounds. We overexpressed hEST1 in Escherichia coli in fusion with GST, then purified the enzyme using a glutathione affinity column, and obtained GST-free enzyme by digestion with thrombin. Using [35S]-phosphosadenosine phosphosulfate (PAPS) as cofactor, we showed that hEST1 efficiently metabolizes the transformation of 2-OH-E2 and 2-OH-E1. However, the transformation of 4-OH-E1 and 4-OH-E2 is much less efficient. Our results also show that hEST1 metabolizes more efficiently E2 than E1. Since hEST1 mRNA is produced from the same gene as MPST using different alternative promoters and since it is expressed in most breast cancer cells (MCF-7, ZR-75-1, T47-D, MDA-231, and MDA-418), studies of the expression and activity of hEST1 will be most important to have a better knowledge about its involvement in the control of the genotoxicity of estrogens and catecholestrogens.

Base Sequence↗
PubMed2001

Modulation of the androgenic response by recombinant human 11-cis retinol dehydrogenase.

The 11-cis retinol dehydrogenase (11-cis-RoDH) enzyme catalyzes the oxidation of cis-retinols to their respective retinals, a rate limiting step in the formation of retinoic acids. Earlier, we have shown that the enzyme also exhibits an oxidative 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) activity that can convert 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) into dihydrotestosterone (DHT), the most potent natural androgen. 11-cis-RoDH could thus control the formation of two active hormones, namely 9-cis retinoic acid and DHT. Therefore, depending upon the substrate availability in the various tissues, this enzyme could provide different metabolites for specific cell functions. To further investigate the role of 11-cis-RoDH in the formation of DHT from 3alpha-diol, we stably expressed the enzyme in the human embryonic kidney cell line 293 (HEK-293). The transformation of 3alpha-diol by these cells was evaluated by assays using both microsomal fractions and intact cultured cells stably expressing 11-cis-RoDH. The results show that in the intact cells 11-cis-RoDH only catalyzes the oxidation of 3alpha-diol into DHT whereas the microsomal fraction catalyzes both the oxidation and the reduction reactions depending upon whether NAD(+) or NADH is added. Furthermore, we examined the ability of 11-cis-RoDH, through the production from 3alpha-diol of the active androgen DHT, to activate the androgen-responsive promoter of the prostate-specific antigen (PSA) gene. The co-transfection of the pCMV expression vector containing 11-cis-RoDH (pCMV-11-cisRoDH), a luciferase reporter gene driven by a PSA promoter (pCMV-PSA-Luc) and an androgen receptor (pCMV-hAR) showed that, in the presence of 3alpha-diol, the expression of the PSA promoter is increased by five to six-fold. Moreover, this stimulatory effect is inhibited by hydroxyflutamide, a well-known antiandrogen. These results suggest that 11-cis-RoDH could be involved in a non-classical pathway of androgen formation and might play a role in the modulation of the androgenic response in some peripheral tissues.

Alcohol Oxidoreductases↗
PubMed2001

Comparative biosynthetic pathway of androstenol and androgens.

It has been shown recently that androstenol and androstanol could modulate gene expression through the nuclear orphan receptors CAR (constitutive androstane receptor) and PXR (pregnane X receptor). Although, in the pig, androstenol is produced in high amounts and is active as a pheromone, its role in the human is ill defined. Androstenol possesses a structure similar to that of androgens, with the exception that it does not possess an oxygen at position 17 that is crucial for androgenic and estrogenic activity. It has been shown that human and boar testis homogenates could produce androstenol, but details of the biosynthetic pathway had not yet been elucidated. It has also been shown recently that androstenol could modulate the activity of CAR and PXR and the expression of some cytochrome P450 drug-metabolizing enzymes. We wanted to determine the precise biosynthetic pathway of androstenol and other closely related steroids. Using transformed human embryonic kidney (HEK-293) cells that stably express 3 beta-hydroxysteroid dehydrogenase, 5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase, we have shown that these enzymes are able to efficiently transform the precursor 5,16-androstadien-3 beta-ol into androstenol. We thus provided evidence that androstenol, the ligand for CAR and PXR, is produced by the biosynthetic pathway of sex steroids.

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

Parallel solid-phase synthesis of 3beta-peptido-3alpha-hydroxy-5alpha-androstan-17-one derivatives for inhibition of type 3 17beta-hydroxysteroid dehydrogenase.

Type 3 17beta-hydroxysteroid dehydrogenase (17beta-HSD), a key steroidogenic enzyme, transforms 4-androstene-3,17-dione (Delta(4)-dione) into testosterone. In order to produce potential inhibitors, we performed solid-phase synthesis of model libraries of 3beta-peptido-3alpha-hydroxy-5alpha-androstan-17-ones with 1, 2, or 3 levels of molecular diversity, obtaining good overall yields (23-58%) and a high average purity (86%, without any purification steps) using the Leznoff's acetal linker. The libraries were rapidly synthesized in a parallel format and the generated compounds were tested as inhibitors of type 3 17beta-HSD. Potent inhibitors were identified from these model libraries, especially six members of the level 3 library having at least one phenyl group. One of them, the 3beta-(N-heptanoyl-L-phenylalanine-L-leucine-aminomethyl)-3alpha-hydroxy-5alpha-androstan-17-one (42) inhibited the enzyme with an IC(50) value of 227nM, which is twice as potent as the natural substrate Delta(4)-dione when used itself as an inhibitor. Using the proliferation of androgen-sensitive (AR(+)) Shionogi cells as model of androgenicity, the compound 42 induced only a slight proliferation at 1 microM (less than previously reported type 3 17beta-HSD inhibitors) and, interestingly, no proliferation at 0.1 microM.

17-Hydroxysteroid Dehydrogenases↗
PubMed2001

The octadecaneuropeptide ODN stimulates neurosteroid biosynthesis through activation of central-type benzodiazepine receptors.

Neurosteroids may play a major role in the regulation of various neurophysiological and behavioural processes. However, while the biochemical pathways involved in the synthesis of neuroactive steroids in the central nervous system are now elucidated, the mechanisms controlling the activity of neurosteroid-producing cells remain almost completely unknown. In the present study, we have investigated the effect of the octadecaneuropeptide (ODN), an endogenous ligand of benzodiazepine receptors, in the control of steroid biosynthesis in the frog hypothalamus. Glial cells containing ODN-like immunoreactivity were found to send their thick processes in the close vicinity of neurones expressing the steroidogenic enzyme 3 beta-hydroxysteroid dehydrogenase. Exposure of frog hypothalamic explants to graded concentrations of ODN (10(-10)-10(-5) M) produced a dose-dependent increase in the conversion of tritiated pregnenolone into various radioactive steroids, including 17-hydroxypregnenolone, progesterone, 17-hydroxyprogesterone, dehydroepiandrosterone and dihydrotestosterone. The ODN-induced stimulation of neurosteroid biosynthesis was mimicked by the central-type benzodiazepine receptor (CBR) inverse agonists methyl beta-carboline-3-carboxylate (beta-CCM) and methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM). The stimulatory effects of ODN, beta-CCM and DMCM on steroid formation was markedly reduced by the CBR antagonist flumazenil. The ODN-evoked stimulation of neurosteroid production was also significantly attenuated by GABA. Collectively, these data indicate that the endozepine ODN, released by glial cell processes in the vicinity of 3 beta-hydroxysteroid dehydrogenase-containing neurones, stimulates the biosynthesis of neurosteroids through activation of central-type benzodiazepines receptors.

17-alpha-Hydroxypregnenolone↗
PubMed2001

Crystallization and preliminary X-ray crystallographic analysis of the human type 3 3 alpha-hydroxysteroid dehydrogenase at 1.8 A resolution.

In androgen-sensitive target tissues, 3 alpha-hydroxysteroid dehydrogenase regulates the androgen receptor (AR) activity by catalyzing the inactivation of 5 alpha-dihydrotestosterone (the most natural potent androgen) to 5 alpha-androstane-3 alpha,17 beta-diol. In this report, the crystallization of a human prostatic type 3 3 alpha-hydroxysteroid dehydrogenase, a member of the aldo-keto reductase superfamily, is described. Two different crystal forms of the complex between the human type 3 3 alpha-HSD, NADP(+) and testosterone have been obtained using PEG as precipitant. Crystal form I, which diffracts to 1.6 A, belongs to the monoclinic space group P2(1), with unit-cell parameters a = 55.07, b = 87.15, c = 76.88 A, beta = 107.37 degrees and two subunits in the asymmetric unit. A complete data set has been collected at 1.8 A. Crystal form II, which diffracts to 2.6 A, belongs to the rhombohedral space group R32, with unit-cell parameters a = b = 143.59, c = 205.86 A, alpha = beta = 90, gamma = 120 degrees and two subunits in the asymmetric unit.

3-Hydroxysteroid Dehydrogenases↗