Publications

• DHRS7 (SDR34C1) - A new player in the regulation of androgen receptor function by inactivation of 5alpha-dihydrotestosterone?

  Araya S., Kratschmar D.V., Tsachaki M., Stuecheli S., Beck K.R., Odermatt A.

  DHRS7 (SDR34C1) has been associated with potential tumor suppressor effects in prostate cancer; however, its function remains largely unknown. Recent experiments using purified recombinant human DHRS7 suggested several potential substrates, including the steroids cortisone and Δ4-androstene-3,17-d ... >> More

  DHRS7 (SDR34C1) has been associated with potential tumor suppressor effects in prostate cancer; however, its function remains largely unknown. Recent experiments using purified recombinant human DHRS7 suggested several potential substrates, including the steroids cortisone and Δ4-androstene-3,17-dione (androstenedione). However, the substrate and cofactor concentrations used in these experiments were very high and the physiological relevance of these observations needed to be further investigated. In the present study, recombinant human DHRS7 was expressed in intact HEK-293 cells in order to investigate whether glucocorticoids and androgens serve as substrates at sub-micromolar concentrations and at physiological cofactor concentrations. Furthermore, the membrane topology of DHRS7 was revisited using redox-sensitive green-fluorescent protein fusions in living cells. The results revealed that (1) cortisone is a substrate of DHRS7; however, it is not reduced to cortisol but to 20β-dihydrocortisone, (2) androstenedione is not a relevant substrate of DHRS7, (3) DHRS7 catalyzes the oxoreduction of 5α-dihydrotestosterone (5αDHT) to 3α-androstanediol (3αAdiol), with a suppressive effect on androgen receptor (AR) transcriptional activity, and (4) DHRS7 is anchored in the endoplasmic reticulum membrane with a cytoplasmic orientation. Together, the results show that DHRS7 is a cytoplasmic oriented enzyme exhibiting 3α/20β-hydroxysteroid dehydrogenase activity, with a possible role in the modulation of AR function. Further research needs to address the physiological relevance of DHRS7 in the inactivation of 5αDHT and AR regulation. << Less

  J. Steroid Biochem. Mol. Biol. 171:288-295(2017) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Production, purification, and functional analysis of recombinant human and mouse 17beta-hydroxysteroid dehydrogenase type 7.

  Toern S., Nokelainen P., Kurkela R., Pulkka A., Menjivar M., Ghosh S., Coca-Prados M., Peltoketo H., Isomaa V., Vihko P.

  17beta-Hydroxysteroid dehydrogenases (17HSDs) have a central role in the regulation of the biological activity of sex steroid hormones. There is increasing evidence that in addition to their importance in gonads, these hormones also have substantial metabolic roles in a variety of peripheral tissu ... >> More

  17beta-Hydroxysteroid dehydrogenases (17HSDs) have a central role in the regulation of the biological activity of sex steroid hormones. There is increasing evidence that in addition to their importance in gonads, these hormones also have substantial metabolic roles in a variety of peripheral tissues. In the present study, the cDNA of human 17HSD type 7 was cloned. In silico, the gene corresponding to the cDNA was localized on chromosome 1q23, close to the locus of hereditary prostate cancer 1 (HPC1) (1q24-25) and primary open-angle glaucoma (GLC1A) (1q23-25). Further, a pseudogene was found on chromosome 1q44, close to the locus of predisposing for early-onset prostate cancer (PCaP) (1q42.2-43). Both human (h17HSD7) and mouse 17HSD type 7 (m17HSD7) were for the first time produced as recombinant proteins and purified for functional analyses. Further, kinetic parameters and specific activities were described. h17HSD7 converted estrone (E1) to a more potent estrogen, estradiol (E2), and dihydrotestosterone (DHT), a potent androgen, to an estrogenic metabolite 5alpha-androstane-3beta, 17beta-diol (3betaA-diol) equally, thereby catalyzing the reduction of the keto group in either 17- or 3-position of the substrate. Minor 3betaHSD-like activity towards progesterone (P) and 20-hydroxyprogesterone (20-OH-P), leading to the inactivation of P by h17HSD7, was also detected. m17HSD7 efficiently catalyzed the reaction from E1 to E2 and moderately converted DHT to an inactive metabolite 5alpha-androstane-3alpha,17beta-diol (3alphaA-diol) and to an even lesser degree 3betaA-diol. The mouse enzyme did not metabolize P or 20-OH-P. The expression of 17HSD type 7 was observed widely in human tissues, most distinctly in adrenal gland, liver, lung, and thymus. Based on the enzymatic characteristics and tissue distribution, we conclude that h17HSD7 might be an intracrine regulator of steroid metabolism, fortifying the estrogenic milieu in peripheral tissues. << Less

  Biochem. Biophys. Res. Commun. 305:37-45(2003) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Human 3alpha-hydroxysteroid dehydrogenase isoforms (AKR1C1-AKR1C4) of the aldo-keto reductase superfamily: functional plasticity and tissue distribution reveals roles in the inactivation and formation of male and female sex hormones.

  Penning T.M., Burczynski M.E., Jez J.M., Hung C.F., Lin H.K., Ma H., Moore M., Palackal N., Ratnam K.

  The kinetic parameters, steroid substrate specificity and identities of reaction products were determined for four homogeneous recombinant human 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) isoforms of the aldo-keto reductase (AKR) superfamily. The enzymes correspond to type 1 3alpha-HSD (AKR1 ... >> More

  The kinetic parameters, steroid substrate specificity and identities of reaction products were determined for four homogeneous recombinant human 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) isoforms of the aldo-keto reductase (AKR) superfamily. The enzymes correspond to type 1 3alpha-HSD (AKR1C4), type 2 3alpha(17beta)-HSD (AKR1C3), type 3 3alpha-HSD (AKR1C2) and 20alpha(3alpha)-HSD (AKR1C1), and share at least 84% amino acid sequence identity. All enzymes acted as NAD(P)(H)-dependent 3-, 17- and 20-ketosteroid reductases and as 3alpha-, 17beta- and 20alpha-hydroxysteroid oxidases. The functional plasticity of these isoforms highlights their ability to modulate the levels of active androgens, oestrogens and progestins. Salient features were that AKR1C4 was the most catalytically efficient, with k(cat)/K(m) values for substrates that exceeded those obtained with other isoforms by 10-30-fold. In the reduction direction, all isoforms inactivated 5alpha-dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one; 5alpha-DHT) to yield 5alpha-androstane-3alpha,17beta-diol (3alpha-androstanediol). However, only AKR1C3 reduced Delta(4)-androstene-3,17-dione to produce significant amounts of testosterone. All isoforms reduced oestrone to 17beta-oestradiol, and progesterone to 20alpha-hydroxy-pregn-4-ene-3,20-dione (20alpha-hydroxyprogesterone). In the oxidation direction, only AKR1C2 converted 3alpha-androstanediol to the active hormone 5alpha-DHT. AKR1C3 and AKR1C4 oxidized testosterone to Delta(4)-androstene-3,17-dione. All isoforms oxidized 17beta-oestradiol to oestrone, and 20alpha-hydroxyprogesterone to progesterone. Discrete tissue distribution of these AKR1C enzymes was observed using isoform-specific reverse transcriptase-PCR. AKR1C4 was virtually liver-specific and its high k(cat)/K(m) allows this enzyme to form 5alpha/5beta-tetrahydrosteroids robustly. AKR1C3 was most prominent in the prostate and mammary glands. The ability of AKR1C3 to interconvert testosterone with Delta(4)-androstene-3,17-dione, but to inactivate 5alpha-DHT, is consistent with this enzyme eliminating active androgens from the prostate. In the mammary gland, AKR1C3 will convert Delta(4)-androstene-3,17-dione to testosterone (a substrate aromatizable to 17beta-oestradiol), oestrone to 17beta-oestradiol, and progesterone to 20alpha-hydroxyprogesterone, and this concerted reductive activity may yield a pro-oesterogenic state. AKR1C3 is also the dominant form in the uterus and is responsible for the synthesis of 3alpha-androstanediol which has been implicated as a parturition hormone. The major isoforms in the brain, capable of synthesizing anxiolytic steroids, are AKR1C1 and AKR1C2. These studies are in stark contrast with those in rat where only a single AKR with positional- and stereo-specificity for 3alpha-hydroxysteroids exists. << Less

  Biochem. J. 351:67-77(2000) [PubMed] [EuropePMC]

  This publication is cited by 15 other entries.

• Human cytosolic 3alpha-hydroxysteroid dehydrogenases of the aldo-keto reductase superfamily display significant 3beta-hydroxysteroid dehydrogenase activity: implications for steroid hormone metabolism and action.

  Steckelbroeck S., Jin Y., Gopishetty S., Oyesanmi B., Penning T.M.

  The source of NADPH-dependent cytosolic 3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity is unknown to date. This important reaction leads e.g. to the reduction of the potent androgen 5alpha-dihydrotestosterone (DHT) into inactive 3beta-androstanediol (3beta-Diol). Four human cytosolic aldo ... >> More

  The source of NADPH-dependent cytosolic 3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity is unknown to date. This important reaction leads e.g. to the reduction of the potent androgen 5alpha-dihydrotestosterone (DHT) into inactive 3beta-androstanediol (3beta-Diol). Four human cytosolic aldo-keto reductases (AKR1C1-AKR1C4) are known to act as non-positional-specific 3alpha-/17beta-/20alpha-HSDs. We now demonstrate that AKR1Cs catalyze the reduction of DHT into both 3alpha- and 3beta-Diol (established by (1)H NMR spectroscopy). The rates of 3alpha-versus 3beta-Diol formation varied significantly among the isoforms, but with each enzyme both activities were equally inhibited by the nonsteroidal anti-inflammatory drug flufenamic acid. In vitro, AKR1Cs also expressed substantial 3alpha[17beta]-hydroxysteroid oxidase activity with 3alpha-Diol as the substrate. However, in contrast to the 3-ketosteroid reductase activity of the enzymes, their hydroxysteroid oxidase activity was potently inhibited by low micromolar concentrations of the opposing cofactor (NADPH). This indicates that in vivo all AKR1Cs will preferentially work as reductases. Human hepatoma (HepG2) cells (which lack 3beta-HSD/Delta(5-4) ketosteroid isomerase mRNA expression, but express AKR1C1-AKR1C3) were able to convert DHT into 3alpha- and 3beta-Diol. This conversion was inhibited by flufenamic acid establishing the in vivo significance of the 3alpha/3beta-HSD activities of the AKR1C enzymes. Molecular docking simulations using available crystal structures of AKR1C1 and AKR1C2 demonstrated how 3alpha/3beta-HSD activities are achieved. The observation that AKR1Cs are a source of 3beta-tetrahydrosteroids is of physiological significance because: (i) the formation of 3beta-Diol (in contrast to 3alpha-Diol) is virtually irreversible, (ii) 3beta-Diol is a pro-apoptotic ligand for estrogen receptor beta, and (iii) 3beta-tetrahydrosteroids act as gamma-aminobutyric acid type A receptor antagonists. << Less

  J. Biol. Chem. 279:10784-10795(2004) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• The identification of new substrates of human DHRS7 by molecular modeling and in vitro testing.

  Zemanova L., Kirubakaran P., Pato I.H., Stambergova H., Vondrasek J.

  Human DHRS7 (SDR34C1) is one of insufficiently described enzymes of the short-chain dehydrogenase/reductase superfamily. The members of this superfamily often play an important pato/physiological role in the human body, participating in the metabolism of diverse substrates (e.g. retinoids, steroid ... >> More

  Human DHRS7 (SDR34C1) is one of insufficiently described enzymes of the short-chain dehydrogenase/reductase superfamily. The members of this superfamily often play an important pato/physiological role in the human body, participating in the metabolism of diverse substrates (e.g. retinoids, steroids, xenobiotics). A systematic approach to the identification of novel, physiological substrates of DHRS7 based on a combination of homology modeling, structure-based virtual screening and experimental evaluation has been used. Three novel substrates of DHRS7 (dihydrotestosterone, benzil and 4,4'-dimetylbenzil) have been described. << Less

  Int. J. Biol. Macromol. 105:171-182(2017) [PubMed] [EuropePMC]

• Human cytosolic hydroxysteroid dehydrogenases of the aldo-ketoreductase superfamily catalyze reduction of conjugated steroids: implications for phase I and phase II steroid hormone metabolism.

  Jin Y., Duan L., Lee S.H., Kloosterboer H.J., Blair I.A., Penning T.M.

  Aldo-ketoreductase 1C (AKR1C) enzymes catalyze the NADPH-dependent reduction of ketosteroids to hydroxysteroids. They are Phase I metabolizing enzymes for natural and synthetic steroid hormones. They convert 5alpha-dihydrotestosterone (Dht, potent androgen) to 3alpha/beta-androstanediols (inactive ... >> More

  Aldo-ketoreductase 1C (AKR1C) enzymes catalyze the NADPH-dependent reduction of ketosteroids to hydroxysteroids. They are Phase I metabolizing enzymes for natural and synthetic steroid hormones. They convert 5alpha-dihydrotestosterone (Dht, potent androgen) to 3alpha/beta-androstanediols (inactive androgens) and the prodrug tibolone (Tib) to estrogenic 3alpha/beta-hydroxytibolones. Herein we demonstrate for the first time that human AKR1C enzymes (AKR1C1-4) are able to reduce conjugated steroids such as Dht-17beta-glucuronide (DhtG), Dht-17beta-sulfate (DhtS), and Tib-17beta-sulfate (TibS). Product identities were characterized by liquid chromatography-mass spectrometry, and kinetic parameters of the reactions were determined. The product profile of the reduction of each steroid conjugate by the individual AKR1C isoform was similar to that of the corresponding free steroid except for the reduction of DhtG catalyzed by AKR1C2, where a complete inversion in stereochemical preference to 3beta-reduction (with DhtG) from 3alpha-reduction (with Dht and DhtS) was observed. The catalytic efficiency of 3-keto reduction was modestly affected by the presence of a 17-sulfate group but severely impaired by the presence of a 17-glucuronide group for AKR1C1-3 isoforms. AKR1C4, however, showed superior catalytic efficiencies versus the other isoforms, and those were unaffected by steroid conjugation. Our findings provide evidence for alternative pathways of steroid metabolism where the phase I reaction (reduction) occurs after the phase II reaction (conjugation). Specifically, it is indicated that Dht is metabolized to its metabolite 3alpha-androstanediol-17-glucuronide via the previously unrecognized "conjugation pathway" involving the sequential reactions of UGT2B17 and AKR1C4 in liver but via the conventional "reduction pathway" involving the sequential reactions of AKR1C2 and UGT2B15/17 in prostate. << Less

  J. Biol. Chem. 284:10013-10022(2009) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.