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R Vihko

Publications and source records attributed to R Vihko.

At least 19 recordsLinked to original sources
PubMed1999

17Beta-hydroxysteroid dehydrogenases in normal human mammary epithelial cells and breast tissue.

17Beta-hydroxysteroid dehydrogenase activity represents a group of several isoenzymes (17HSDs) that catalyze the interconversion between highly active 17beta-hydroxy- and low activity 17-ketosteroids and thereby regulate the biological activity of sex steroids. The present study was carried out to characterize the expression of 17HSD isoenzymes in human mammary epithelial cells and breast tissue. In normal breast tissues 17HSD types 1 and 2 mRNAs were both evenly expressed in glandular epithelium. In two human mammary epithelial cell lines, mRNAs for 17HSD types 1, 2 and 4 were detected. In enzyme activity measurements only oxidative 17HSD activity, corresponding to either type 2 or type 4 enzyme, was present. The role of 17HSD type 4 in estrogen metabolism was further investigated, using several cell lines originating from various tissues. No correlation between the presence of 17HSD type 4 mRNA and 17HSD activity in different cultured cell lines was detected. Instead, oxidative 17HSD activity appeared in cell lines where 17HSD type 2 was expressed and reductive 17HSD activity was present in cells expressing 17HSD type 1. These data strongly suggest that in mammary epithelial cell lines the oxidative activity is due to type 2 17HSD and that oxidation of 17beta-hydroxysteroids is not the primary activity of the 17HSD type 4 enzyme.

17-Hydroxysteroid Dehydrogenases↗
PubMed1999

Identification of essential subelements in the hHSD17B1 enhancer: difference in function of the enhancer and that of the hHSD17BP1 analog is due to -480C and -486G.

The function of the gene encoding human 17beta-hydroxysteroid dehydrogenase (17HSD) type 1, the hHSD17B1 gene, is regulated by a cell-specific enhancer at position -662 to -392. The adjacent hHSD17BP1 gene, whose function is not known, contains an analogous region in its 5'-flanking region. The identity between the hHSD17B1 enhancer and the hHSD17BP1 equivalent is as high as 98%, i.e. they differ by only five nucleotides. Results from reporter gene analyses showed that the hHSD17BP1 analog, a pseudoenhancer, has only 10% the activity of the hHSD17B1 enhancer. Furthermore, the results indicate that the reduced function of the pseudoenhancer is a consequence of the presence of G and A at positions -480 and -486, whereas the hHSD17B1 enhancer contains -480C and -486G. In addition, three protected areas were localized to regions -495/-485 (FP1), -544/-528 (FP2), and -589/-571 (FP3) in deoxyribonuclease I footprinting analysis of the hHSD17B1 enhancer. Replacement of the footprinted regions with a nonsense sequence demonstrated that the FP2 region is the most critical for enhancer activity. Mutations of FP2 or a short palindromic region within it led to almost complete abolishment of enhancer activity. We have identified several subelements that are essential for appropriate function of the hHSD17B1 enhancer. The results also show that the hHSD17B1 and hHSD17BP1 genes operate differently despite the high homology between them.

17-Hydroxysteroid Dehydrogenases↗
PubMed1998

Characterization of rat 17 beta-hydroxysteroid dehydrogenase type 1 gene and mRNA transcripts.

In the present study, the gene encoding rat 17 beta-hydroxysteroid dehydrogenase type 1 (rHSD17B1 gene) was cloned and characterized. Like the analogous human gene (hHSD17B1), rHSD17B1 contains six exons and five introns spanning approximately 2.2 kb. The identity between the exons and introns of the two genes ranges from 58% to 82% and 42% to 57%, respectively. In contrast to hHSD17B1, rHSD17B1 is not duplicated. The cap site for rHSD17B1 was localized to position -41 upstream of the ATG translation initiation codon. Sequence comparison of the first 200 bp upstream of the cap site showed 72% identity between the human and rat HSD17B1 genes, including a conserved GC-rich area. Further upstream, no significant identity between the two genes was observed and several, cis-acting elements known to modulate the expression of hHSD17B1 are not conserved in the rat gene. Rat HSD17B1 unlike hHSD17B1 with two cap sites, possesses two polyadenylation signals, thus resulting in two mRNAs.

17-Hydroxysteroid Dehydrogenases↗
PubMed1998

17Beta-hydroxysteroid dehydrogenase type 1 in normal breast tissue during the menstrual cycle and hormonal contraception.

Our purpose was to assess 17beta-hydroxysteroid dehydrogenase (17HSD) type 1 protein expression in normal breast tissue during the menstrual cycle and hormonal contraception. We analyzed 17HSD type 1 protein expression by immunohistochemistry during the regular menstrual cycle (n = 12) and hormonal contraception (n = 7) in women undergoing reduction mammoplasty. 17HSD type 1 protein was detected in normal breast epithelial cells throughout the menstrual cycle and in all women using hormonal contraception. Mean 17HSD type 1 staining intensity was higher in alveolar epithelial cells in women using hormonal contraception (2.14) than in untreated women (1.25; P < 0.04). For ducts, this difference approached significance (2.29 vs. 1.41; P = 0.06). There was a negative correlation between serum estradiol (E2) levels and 17HSD type 1 protein expression for both alveolar (r(s) = -0.68; P = 0.004) and ductal (r(s) = -0.75; P = 0.002) breast epithelial cells. Enhanced 17HSD type 1 protein expression might increase the conversion to E2 in normal breast tissue during hormonal contraception. The negative correlation between serum E2 levels and 17HSD type 1 suggests this enzyme to be one of the regulatory mechanisms of intratissue E2 concentration in normal breast tissue.

17-Hydroxysteroid Dehydrogenases↗
PubMed1998

Expression cloning of a novel estrogenic mouse 17 beta-hydroxysteroid dehydrogenase/17-ketosteroid reductase (m17HSD7), previously described as a prolactin receptor-associated protein (PRAP) in rat.

17 beta-Hydroxysteroid dehydrogenases/17-ketosteroid reductases (17HSDs) modulate the biological activity of certain estrogens and androgens by catalyzing reductase or dehydrogenase reactions between 17-keto- and 17 beta-hydroxysteroids. In the present study, we demonstrate expression cloning of a novel type of 17HSD, chronologically named 17HSD type 7, from the HC11 cell line derived from mouse mammary gland. The cloned cDNA, 1.7 kb in size, encodes a protein of 334 amino acids with a calculated molecular mass of 37,317 Da. The primary structure contains segments characteristic of enzymes belonging to the short-chain dehydrogenase/reductase superfamily. Strikingly, mouse 17HSD type 7 (m17HSD7) shows 89% identity with a recently cloned rat protein called PRL receptor-associated protein (PRAP). The function of PRAP has not yet been demonstrated. The enzymatic characteristics of m17HSD7 and RT-PCR-cloned rat PRAP (rPRAP) were analyzed in cultured HEK-293 cells, where both of the enzymes efficiently catalyzed conversion of estrone (E1) to estradiol (E2). With other substrates tested no detectable 17HSD or 20 alpha-hydroxysteroid dehydrogenase activities were found. Kinetic parameters for m17HSD7 further indicate that E1 is a preferred substrate for this enzyme. Relative catalytic efficiencies (Vmax/K(m) values) for E1 and E2 are 244 and 48, respectively. As it is the case with rPRAP, m17HSD7 is most abundantly expressed in the ovaries of pregnant animals. Further studies show that the rat enzyme is primarily expressed in the middle and second half of pregnancy, in parallel with E2 secretion from the corpus luteum. The mRNA for m17HSD7 is also apparent in the placenta, and a slight signal for m17HSD7 is found in the ovaries of adult nonpregnant mice, in the mammary gland, liver, kidney, and testis. Altogether, because of their similar primary structures, enzymatic characteristics, and the tissue distribution of m17HSD7 and rPRAP, we suggest that rPRAP is rat 17HSD type 7. Furthermore, the results indicate that 17HSD7 is an enzyme of E2 biosynthesis, which is predominantly expressed in the corpus luteum of the pregnant animal.

17-Hydroxysteroid Dehydrogenases↗
PubMed1998

Inhibition of 17beta-hydroxysteroid oxidoreductase by flavonoids in breast and prostate cancer cells.

Several flavonoids and isoflavonoids were found to inhibit 17beta-oxidoreduction of estrogens by the purified 17beta-HSOR type 1, or in cell lines expressing 17beta-HSOR type 1 enzyme (T-47D breast cancer cells) or type 2 (PC-3 prostate cancer cells). The structural demands for the inhibition of estrone (E1) reduction and estradiol (E2) oxidation catalyzed by 17beta-HSOR types 1 and 2, respectively, were not identical. Flavones, flavanones, and isoflavones hydroxylated at both the double ring (positions 5 and 7) and ring B (position 4') were the most potent inhibitors of E1 reduction in T-47D cells, and by the purified type 1 enzyme whereas flavones hydroxylated at positions 3, 5, and 7 of rings A and C, with or without a hydroxyl group in ring B, were capable of inhibiting E2 oxidation in PC-3 cells. Change to flavanone structure, or hydroxylation at position 3 of ring C of flavones, or methylation of the hydroxyl group at position 4' of ring B of flavones and isoflavones reduced or abolished their inhibitory activity on E1 reduction in T-47D cells. On the contrary, hydroxyl group at position 3 of flavones (flavonol structure) markedly increased the inhibition of E2 oxidation in PC-3 cells. Thus, changes in the number and location of hydroxyl groups may discriminate inhibition of E1 reduction and E2 oxidation. Some of the differences may be due to differences in pharmacokinetics of these compounds in T-47D and PC-3 cells. Inhibition of 17beta-HSORs could lead to an alteration in the availability of the highly active endogenous estrogen, but the effects of these compounds in vivo cannot be predicted on the basis of these results alone. Some of these compounds (isoflavones) are estrogenic per se, and they may replace endogenous estrogens, whereas flavones are only very weakly estrogenic or nonestrogenic. Regarding prevention or treatment of estrogen-related diseases, apigenin, coumestrol, and genistein raise special interest.

17-Hydroxysteroid Dehydrogenases↗
PubMed1997

Growth factors and phorbol-12-myristate-13-acetate modulate the follicle-stimulating hormone- and cyclic adenosine-3',5'-monophosphate-dependent regulation of 17beta-hydroxysteroid dehydrogenase type 1 expression in rat granulosa cells.

In the present study primary cultures of rat granulosa cells obtained from diethylstilbestrol (DES)-primed immature rats were used to study the regulation of 17beta-hydroxysteroid dehydrogenase (17HSD) activity and type 1 expression via protein kinase A (PKA)- and C (PKC)-dependent pathways, and by several autocrine and/or paracrine growth factors. Follicle-stimulating hormone (FSH), 8-bromo-cyclic adenosine-3',5'-monophosphate (8-Br-cAMP) and transforming growth factor beta1 (TGFbeta1) strongly enhanced 17HSD activity and type 1 expression. The stimulatory effects of FSH and 8-Br-cAMP were further potentiated by TGFbeta1. In contrast, neither phorbol-12-myristate-13-acetate (PMA), epidermal growth factor (EGF), transforming growth factor alpha (TGFalpha) nor fibroblast growth factor (bFGF) affected 17HSD activity or type 1 expression when given alone. However, they effectively neutralized the stimulatory effects of 8-Br-cAMP and FSH. The present data suggest that, in rat granulosa cells 17HSD type 1 expression is primarily induced by FSH acting via PKA-dependent pathway and the extent of the induction is modulated by PKC-dependent inhibition and autocrine/paracrine growth factors present in the ovary.

17-Hydroxysteroid Dehydrogenases↗
PubMed1997

Ontogeny of 17beta-hydroxysteroid dehydrogenase type 2 mRNA expression in the developing mouse placenta and fetus.

17beta-Hydroxysteroid dehydrogenase type 2 (17HSD type 2) catalyzes the inactivation of estradiol, testosterone and dihydrotestosterone into biologically less active 17-keto forms. Our recent Northern analysis indicated that the enzyme is expressed both in mouse placenta and fetus. The present data indicate that in the placenta the distribution of enzyme expression changes during pregnancy. In the choriovitelline placenta (day 8) 17HSD type 2 was expressed both in mural and polar giant cells. Later, on days 9-12.5, the mRNA was also detected in the junctional zone, and in late gestation (days 14.5-17.5), 17HSD type 2 mRNA was predominantly expressed only at the labyrinth region. In the fetus, 17HSD type 2 expression appears in the liver on day 11. At day 12 the expression was strongly increased in the liver, and at the same time moderate mRNA expression was also detected in the esophagus and intestine. In these tissues, high constitutive expression of 17HSD type 2 was then maintained throughout pregnancy. At later stages of development (days 15-16) the mRNA was, furthermore, detected in epithelial cells of the stomach, tongue, oropharynx and nasopharynx as well as in the kidney. We conclude that the expression pattern of 17HSD type 2 in the developing placenta and fetus suggests a role for the enzyme in maintaining a barrier to the transfer of active 17-hydroxy forms of sex steroids between the fetus and maternal circulation.

17-Hydroxysteroid Dehydrogenases↗
PubMed1997

Loss of heterozygosity at 16q24.1-q24.2 is significantly associated with metastatic and aggressive behavior of prostate cancer.

Several studies have indicated that in prostate cancer, frequent aberrations take place in several genomic regions. In the present study, we have analyzed allelic losses in chromosome 16 region q in 50 prostate cancer specimens of various histological grades. The most frequently deleted region was located at 16q23-16q24.2 between loci D16S504 and D16S422. The highest percentage of loss of heterozygosity (LOH) at 16q was also found within this area at loci HSD17B2 and D16S422 located at 16q24.1-q24.2. The LOH at 16q24.1-q24.2 was significantly associated with clinically aggressive behavior of the disease, metastatic disease, and higher tumor grade. Of the metastatic diseases, 83% showed LOH, whereas only 40% of the nonmetastatic diseases were found to show it. Similarly, LOH was found in 76% of the clinically aggressive diseases and in 33% of the nonaggressive diseases. The data suggest that a potentially important gene associated with prostate cancer progression is located close to 16q24.1-q24.2.

Chromosome Mapping↗
PubMed1997

Retinoic acids increase 17 beta-hydroxysteroid dehydrogenase type 1 expression in JEG-3 and T47D cells, but the stimulation is potentiated by epidermal growth factor, 12-O-tetradecanoylphorbol-13-acetate, and cyclic adenosine 3',5'-monophosphate only in JEG-3 cells.

Human 17 beta-hydroxysteroid dehydrogenase type 1 (17HSD type 1) primarily catalyzes the reduction of low activity estrone to high activity estradiol in ovarian granulosa cells and placental trophoblasts 17HSD type 1 is also present in certain peripheral tissues, such as breast tissue. In the present study we investigated the effects of retinoic acids (RAs) together with other stimuli known to modulate estradiol production and/or cell growth on expression of 17HSD type 1 in JEG-3 choriocarcinoma cells and estrogen-responsive T47D breast cancer cells. Treatment of cultured JEG-3 and T47D cells with all-trans-RA and 9-cis-RA increased reductive 17HSD activity and 17HSD type 1 messenger RNA expression severalfold in both cell lines. On the other hand, epidermal growth factor (EGF), Ca ionophore, the protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate (TPA), and cAMP elevated 17HSD type 1 expression only in JEG-3 cells. Correspondingly, the effects of RAs were potentiated by EGF, TPA, and cAMP in JEG-3 cells, whereas no such phenomenon was observed in T47D cells. In JEG-3 cells, simultaneous administration of RAs with TPA and EGF maximally resulted in approximately 40- and 20-fold increases in 17HSD type 1 messenger RNA expression, respectively. The present data indicate that RAs may stimulate estradiol biosynthesis by regulating 17HSD type 1 expression in certain breast cancer and choriocarcinoma cells. The results suggest that interaction of multiple regulatory pathways is involved in maintaining high 17HSD type 1 expression in the placenta. In addition, regulation of 17HSD type 1 expression may be different in trophoblast cells from that in breast epithelial cells.

17-Hydroxysteroid Dehydrogenases↗
PubMed1997

Expression of 17beta-hydroxysteroid dehydrogenase type 1 and type 2, P450 aromatase, and 20alpha-hydroxysteroid dehydrogenase enzymes in immature, mature, and pregnant rats.

In the present study, we evaluated the expression and regulation of 17beta-hydroxysteroid dehydrogenase (17HSD) type 1 and type 2, cytochrome P450 aromatase (P450arom), and 20alpha-hydroxysteroid dehydrogenase (20HSD) in mature and pregnant rats. Immunohistochemical analysis of rat 17HSD type 1 showed that the enzyme is exclusively expressed in the granulosa cells of developing, healthy, primary, secondary, and tertiary follicles at all stages of the estrous cycle and pregnancy, and is not detected in the corpora lutea. The data showed that the amount of the enzyme expressed in the follicle increases as follicular maturation progresses and is highest in tertiary and Graafian follicles. However, Northern blot analysis of total RNA from whole ovaries showed a rather constitutive expression of the 17HSD type 1 enzyme. It is evident that compared with P450arom, 17HSD type 1 is more widely expressed in the follicles during the various maturational stages of folliculogenesis. Hence, the data indicate distinct localization, expression, and regulation patterns for 17HSD type 1 and P450arom during the rat estrous cycle and pregnancy. Furthermore, compared with the two estradiol biosynthetic enzymes, a different expression pattern was detected for 20HSD messenger RNA. During the estrous cycle the enzyme was detected in the ovaries throughout the cycle, and in the ovaries of pregnant animals the enzyme showed an expression pattern the opposite of that observed for P450arom. Rat 17HSD type 2, not detected in the ovaries, was constitutively expressed in both female and male liver and small intestine in 21-day-old fetuses up to 6-week-old mature animals. Similarly, in these tissues the enzyme was constitutively expressed in normal cycling and pregnant animals, but it showed increasing expression in the placenta as pregnancy advanced. The relatively constitutive expression of the enzyme at all physiological stages of the animals suggests a general role for the enzyme in the inactivation of circulating sex steroids.

17-Hydroxysteroid Dehydrogenases↗
PubMed1997

Origin of substrate specificity of human and rat 17beta-hydroxysteroid dehydrogenase type 1, using chimeric enzymes and site-directed substitutions.

Human 17beta-hydroxysteroid dehydrogenase (17-HSD) type 1 predominantly catalyzes the 17beta-reduction of estrone to estradiol. The present results, however, show that rat 17-HSD type 1 equally uses both estrone and androstenedione as substrates. Analyzing the activity of various rat/human chimeric enzymes indicated that the region between amino acids 148 and 268 is responsible for the difference in substrate specificity, which is in line with the structural data showing that the recognition end of the active site is primarily at residues 185-230. The enzymes are highly conserved between amino acids 148-191, and the data indicate that in this region Asn152HisAsp153Glu and Pro187Ala variations are most closely related to the differential steroid specificity. The structural analyses furthermore suggested that the presence of His instead of Asn at position 152 of the human enzyme might result in considerable rearrangement of the loop located close to the beta-face of the A- and B-rings of the bound substrate, and that the Pro187Ala variation could modify the flexible region involved in substrate recognition and access of the substrate to the active site. Altogether, our results indicate that the Asn152His and Pro187Ala variations, together with several amino acid variations at the recognition end of the catalytic cleft built by residues 190-230, alter the structure of the active site of rat 17-HSD type 1 to one more favorable to an androgenic substrate.

Amino Acid Sequence↗
PubMed1997

The proximal promoter region of the gene encoding human 17beta-hydroxysteroid dehydrogenase type 1 contains GATA, AP-2, and Sp1 response elements: analysis of promoter function in choriocarcinoma cells.

The 5'-flanking region from -78 to +9 in the HSD17B1 gene serves as a promoter, and an HSD17B1 silencer element is located in position -113 to -78. In the present studies, we have characterized three regulatory elements in the proximal 5'-flanking regions of the gene, using electrophoretic mobility shift assays and reporter gene analysis. First, nuclear factors recognized by antibodies against Sp1 and Sp3 were found to bind the Sp1 motif in the region from -52 to -43. Mutation of the Sp1-binding site decreased the promoter activity to 30% in JEG-3 cells and to 60% in JAR cells, suggesting that binding to the Sp1 motif has a substantial role in the complete functioning of the HSD17B1 promoter. Second, the binding of AP-2 to its motif in the region from -62 to -53 led to reduced binding of Sp1 and Sp3, and furthermore, mutation of the AP-2 element increased promoter activity to 260% in JEG-3 cells. The data thus implied that AP-2 can repress the function of the HSD17B1 promoter by preventing binding to the Sp1 motif. Finally, GATA factors, GATA-3 in particular, were demonstrated to bind their cognate sequence in the HSD17B1 silencer region, and mutations introduced into the GATA-binding site increased transcriptional activity to the level seen in constructs not containing the silencer element. Thus, GATA-3 seems to prevent transcription in the constructs, and hence, the GATA motif also may operate as a negative control element for HSD17B1 transcription.

Base Sequence↗
PubMed1997

Characterization of structural and functional properties of human 17 beta-hydroxysteroid dehydrogenase type 1 using recombinant enzymes and site-directed mutagenesis.

Human 17 beta-hydroxysteroid dehydrogenase (17-HSD) type 1 catalyzes the conversion of the low activity estrogen, estrone, into highly active estradiol, both in the gonads and in target tissues. The present study was carried out to characterize the dimerization, microheterogeneity, and phosphorylation of human 17-HSD type 1 and to evaluate the current model of hydride transfer and substrate recognition of the enzyme, based on its x-ray structure. 17-HSD type 1 is a homodimer consisting of noncovalently bound subunits, and the data in the present study indicate an exceptionally strong association between the monomers [dissociation constant (Kd) < 5 pmol/monomers liter]. Furthermore, substitutions constructed at the hydrophobic dimer interface always resulted in inactive aggregates of the protein. The enzyme was shown to be phosphorylated by protein kinase A exclusively at Ser134 only in vitro. However, in contrast to previous suggestions, phosphorylation of Ser134 was shown to play no role in the activity or microheterogeneity of human 17-HSD type 1. The presence of microheterogeneity in the recombinant enzyme also indicates that it does not result from the frequent protein polymorphism previously found for the enzyme. In line with the x-ray structure and the proposed catalytic mechanism of the enzyme, our results indicate that Ser142, Tyr155, and Lys159 are all critical for hydride transfer in human 17-HSD type 1. In contrast, the proposed interaction between His221, Glu282, and the 3-OH group of the steroid at the substrate recognition helix could not be shown to exist. Neither of these residues plays a critical role in the catalytic action of the enzyme in cultured cells.

Binding Sites↗
PubMed1996

Characterization of 17beta-hydroxysteroid dehydrogenase isoenzyme expression in benign and malignant human prostate.

In the present study, expressions of 17beta-hydroxysteroid dehydrogenase (17HSD) types 1, 2, and 3, 5alpha-reductase type 2 and human androgen receptor mRNAs were determined in 12 benign prostatic hyperplasia and 17 prostatic carcinoma specimens. 17HSD type 2 was found to be the principle isoenzyme expressed in the prostate. Significantly higher expressions of 17HSD type 2 and 5alpha-reductase type 2 were detected in benign prostatic hyperplasia compared with the carcinoma specimens. Expression of the androgen receptor in the 2 groups was not significantly different. 17HSD type 3 mRNA was not detected in any of the specimens investigated. Only low constructive expression of the 2.3 kb mRNA of 17HSD type 1 was seen. Immunohistochemical analysis indicated that this did not lead to significant enzyme expression, only faint staining for the enzyme protein being detected, mainly in uroepithelial cells. No significant correlation was found between any of the mRNAs analysed, but the data on 5alpha-reductase type 2 mRNA support the presence of an increased proportion of 5alpha-dihydrotesterone in the hyperplastic prostate. In cultured PC-3 prostatic cancer cells and in the transiently transfected human embryonic kidney 293 cells, 17HSD type 2 was found exclusively to convert 5alpha-dihydrotestosterone and testosterone into the less potent 17-keto compounds 5alpha-androstanedione and 4-androstenedione, respectively. We suggest that the 17HSD type 2 isoenzyme plays a part in the metabolic pathway, resulting in the inactivation of testosterone and 5alpha-dihydrotestosterone locally in the prostate. The enzyme expressed in the prostate could, therefore, protect cells from excessive androgen action.

17-Hydroxysteroid Dehydrogenases↗
PubMed1996

Molecular cloning of mouse 17 beta-hydroxysteroid dehydrogenase type 1 and characterization of enzyme activity.

The biological activity of certain estrogens and androgens is modulated by enzymes called 17 beta-hydroxysteroid dehydrogenases (17 beta-HSDs), which catalyze the interconversion between less active 17-oxosteroid and more active 17 beta-hydroxysteroid forms. In the present report, we describe cloning of mouse 17 beta-HSD type-1 cDNA from an ovarian library generated from 4,4'-(1,2-diethyl-1,2-ethenediyl)bisphenol-(diethylstilbestrol)-tr eated mice, and characterization of the corresponding enzyme. The open reading frame of the mouse 17 beta-HSD type-1 cDNA encodes a peptide of 344 amino acid residues with a predicted molecular mass of 36785 Da. The mouse 17 beta-HSD type-1 enzyme shares 63% and 93% overall identity with human and rat 17 beta-HSD type-1 enzymes, respectively, and the most striking differences between the mouse and human type-1 enzymes are between the amino acid residues 197 and 230 and in the carboxy terminus of the enzymes. Similarly to the human 17 beta-HSD type-1 enzyme, the mouse type-1 enzyme primarily catalyzes reductive reactions from 17-oxo forms to 17 beta-hydroxy forms in intact cultured cells, but unlike the human type-1 enzyme, the mouse enzyme does not prefer phenolic over neutral substrates. Thus, mouse 17 beta-HSD type 1 catalyzes reduction of androst-4-ene-3,17-dione (androstenedione) to 17 beta-hydroxyandrost-4-en-3-one (testosterone) as efficiently as 3 beta-hydroxyestra-1,3,5(10)-trien-17-one (estrone) to estra-1,3,5(10)-triene-3 beta, 17 beta-diol (estradiol). 17 beta-HSD type 1 is predominantly expressed in mouse ovaries, in which it is located in granulosa cells.

17-Hydroxysteroid Dehydrogenases↗
PubMed1996

Cloning of rat 17 beta-hydroxysteroid dehydrogenase type 2 and characterization of tissue distribution and catalytic activity of rat type 1 and type 2 enzymes.

17 beta-Hydroxysteroid dehydrogenases (17HSDs) are enzymes catalyzing the conversion between 17 beta-hydroxy- and 17-ketosteroids. Both estrogens and androgens possess their highest activity in the 17 beta-hydroxy form, and the enzymes, therefore, regulate the biological activity of sex hormones. In this study, we have characterized the complementary DNA (cDNA) for rat 17HSD type 2. The cDNA encodes a protein with a predicted mol wt of 42,010 Da. The protein has 77% similarity and 62% identity with the human 17HSD type 2 enzyme. Furthermore, the hydropathicity profiles of the enzymes are very similar. The two isozymes contain a putative transmembrane region close to the N-terminus. However, the rat isozyme lacks the two lysine-rich amino acid cluster present at the N- and C-terminals of human 17HSD type 2. The tissue distribution of the rat 17HSD type 1 and type 2 enzymes is very similar to that of the human enzymes. The highest expression of 17HSD type 2 was detected in the placenta. In addition, a 1.5-kilobase messenger RNA for the enzyme was detected in the small intestine, liver, and kidney of both sexes. The two messenger RNAs for rat 17HSD type 1 (1.4 and 1.7 kilobases) were highly expressed only in the ovary, and at very low concentrations in the kidney of both sexes. Transiently expressed rat 17HSD type 2 showed oxidative activity almost exclusively in cultured human embryonic kidney 293 cells, converting estradiol into estrone and testosterone into androstenedione, whereas the opposite was observed for the rat type 1 enzyme. The data suggest that similarly to the corresponding human isoforms, rat 17HSD type 2 is mostly involved in the oxidation of 17 beta-hydroxysteroids into their relatively inactive keto derivative in peripheral tissues, whereas rat 17HSD type 1 is mainly involved in the glandular biosynthesis of estradiol.

17-Hydroxysteroid Dehydrogenases↗