Publications

• Characterization of 5alpha-reductase activity and isoenzymes in human abdominal adipose tissues.

  Fouad Mansour M., Pelletier M., Tchernof A.

  <h4>Introduction</h4>The substrate for the generation of 5α-dihydrotestosterone (DHT) is either androstenedione (4-dione) which is first converted to androstanedione and then to DHT through 17-oxoreductase activity, or testosterone, which is directly converted to DHT. Three 5α-reductase isoenzymes ... >> More

  <h4>Introduction</h4>The substrate for the generation of 5α-dihydrotestosterone (DHT) is either androstenedione (4-dione) which is first converted to androstanedione and then to DHT through 17-oxoreductase activity, or testosterone, which is directly converted to DHT. Three 5α-reductase isoenzymes have been characterized and designated as types 1, 2 and 3 (SRD5A1, 2 and 3).<h4>Objective</h4>To define the predominant source of local DHT production in human adipose tissues, identify 5α-reductase isoenzymes and test their impact on preadipocyte differentiation.<h4>Methods</h4>Cultures of omental (OM) and subcutaneous (SC) preadipocytes were treated for 0, 6 or 24h with 30nM (14)C-4-dione or (14)C-testosterone, with and without 500nM 5α-reductase inhibitors 17-N,N-diethylcarbamoyl-4-methyl-4-aza-5-androstan-3-one (4-MA) or finasteride. Protein level and mRNA abundance of 5α-reductase isoenzymes/transcripts were examined in whole SC and OM adipose tissue. HEK-293 cells stably transfected with 5α-reductase type 1, 2 or 3 were used to test 5α-reductase inhibitors. We also assessed the impact of 5α-reductase inhibitors on preadipocyte differentiation.<h4>Results</h4>Over 24h, DHT formation from 4-dione increased gradually (p<0.05) and was significantly higher compared to that generated from testosterone (p<0.001). DHT formation from both 4-dione and testosterone was blocked by both 5α-reductase inhibitors. In whole adipose tissue from both fat compartments, SRD5A3 was the most highly expressed isoenzyme followed by SRD5A1 (p<0.001). SRD5A2 was not expressed. In HEK-293 cells, 4-MA and finasteride inhibited activity of 5α-reductases types 2 and 3 but not type 1. In preadipocyte cultures where differentiation was inhibited by 4-dione (p<0.05, n=7) or testosterone (p<0.05, n=5), the inhibitors 4-MA and finasteride abolished these effects.<h4>Conclusion</h4>Although 4-dione is the main source of DHT in human preadipocytes, production of this steroid by 5α-reductase isoenzymes mediates the inhibitory effect of both 4-dione and testosterone on preadipocyte differentiation. << Less

  J. Steroid Biochem. Mol. Biol. 161:45-53(2016) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Biochemical and pharmacogenetic dissection of human steroid 5 alpha-reductase type II.

  Makridakis N.M., di Salle E., Reichardt J.K.

  Human prostatic steroid 5alpha-reductase, encoded by the SRD5A2 gene on chromosome band 2p23, catalyses the irreversible conversion of testosterone to dihydrotestosterone (DHT), the most active androgen in the prostate, with NADPH as its cofactor. This enzyme has never been purified but a number o ... >> More

  Human prostatic steroid 5alpha-reductase, encoded by the SRD5A2 gene on chromosome band 2p23, catalyses the irreversible conversion of testosterone to dihydrotestosterone (DHT), the most active androgen in the prostate, with NADPH as its cofactor. This enzyme has never been purified but a number of competitive inhibitors have been developed for this enzyme since increased steroid 5alpha-reductase activity may cause benign prostatic hypertrophy and prostate cancer. We report here the detailed biochemical and pharmacogenetic dissection of the human enzyme by analysing 10 missense substitutions and three double mutants which are all naturally found in humans. Nine of these 13 mutants reduce activity (measured as Vmax) by 20% or more, three increase steroid 5alpha-reductase by more than 15% and one results in essentially unaltered kinetic properties suggesting that it is a truly neutral ('polymorphic') amino acid substitution. Substantial pharmacogenetic variation among the mutants was also observed when three competitive inhibitors, finasteride, GG745 (dutasteride) and PNU157706, were investigated. Our studies not only define the substrate and cofactor binding sites of human steroid 5alpha-reductase, but also have significant consequences for the pharmacological usage of steroid 5alpha-reductase inhibitors in human patients treated for prostatic conditions. << Less

  Pharmacogenetics 10:407-413(2000) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Novel 5 alpha-steroid reductase (SRD5A3, type-3) is overexpressed in hormone-refractory prostate cancer.

  Uemura M., Tamura K., Chung S., Honma S., Okuyama A., Nakamura Y., Nakagawa H.

  Prostate cancer often relapses during androgen-depletion therapy, even under conditions in which a drastic reduction of circulating androgens is observed. There is some evidence that androgens remain present in the tissues of hormone-refractory prostate cancers (HRPC), and enzymes involved in the ... >> More

  Prostate cancer often relapses during androgen-depletion therapy, even under conditions in which a drastic reduction of circulating androgens is observed. There is some evidence that androgens remain present in the tissues of hormone-refractory prostate cancers (HRPC), and enzymes involved in the androgen and steroid metabolic pathway are likely to be active in HRPC cells. We previously carried out a genome-wide gene expression profile analysis of clinical HRPC cells by means of cDNA microarrays in combination with microdissection of cancer cells and found dozens of transactivated genes. Among them, we here report the identification of a novel gene, SRD5A2L, encoding a putative 5 alpha-steroid reductase that produces the most potent androgen, 5 alpha-dihydrotestosterone (DHT), from testosterone. Liquid chromatography-tandem mass spectrometry analysis following an in vitro 5 alpha-steroid reductase reaction validated its ability to produce DHT from testosterone, similar to type 1 5 alpha-steroid reductase. Because two types of 5 alpha-steroid reductase were previously reported, we termed this novel 5 alpha-steroid reductase 'type 3 5 alpha-steroid reductase' (SRD5A3). Reverse transcription-polymerase chain reaction and northern blot analyses confirmed its overexpression in HRPC cells, and indicated no or little expression in normal adult organs. Knockdown of SRD5A3 expression by small interfering RNA in prostate cancer cells resulted in a significant decrease in DHT production and a drastic reduction in cell viability. These findings indicate that a novel type 3 5 alpha-steroid reductase, SRD5A3, is associated with DHT production and maintenance of androgen-androgen receptor-pathway activation in HRPC cells, and that this enzymatic activity should be a promising molecular target for prostate cancer therapy. << Less

  Cancer Sci. 99:81-86(2008) [PubMed] [EuropePMC]

• Structural and biochemical properties of cloned and expressed human and rat steroid 5 alpha-reductases.

  Andersson S., Russell D.W.

  The microsomal enzyme steroid 5 alpha-reductase is responsible for the conversion of testosterone into the more potent androgen dihydrotestosterone. In man, this steroid acts on a variety of androgen-responsive target tissues to mediate such diverse endocrine processes as male sexual differentiati ... >> More

  The microsomal enzyme steroid 5 alpha-reductase is responsible for the conversion of testosterone into the more potent androgen dihydrotestosterone. In man, this steroid acts on a variety of androgen-responsive target tissues to mediate such diverse endocrine processes as male sexual differentiation in the fetus and prostatic growth in men. Here we describe the isolation, structure, and expression of a cDNA encoding the human steroid 5 alpha-reductase. A rat cDNA was used as a hybridization probe to screen a human prostate cDNA library. A 2.1-kilobase cDNA was identified and DNA sequence analysis indicated that the human steroid 5 alpha-reductase was a hydrophobic protein of 259 amino acids with a predicted molecular weight of 29,462. A comparison of the human and rat protein sequences revealed a 60% identity. Transfection of expression vectors containing the human and rat cDNAs into simian COS cells resulted in the synthesis of high levels of steroid 5 alpha-reductase enzyme activity. Both enzymes expressed in COS cells showed similar substrate specificities for naturally occurring steroid hormones. However, synthetic 4-azasteroids demonstrated marked differences in their abilities to inhibit the human and rat steroid 5 alpha-reductases. << Less

  Proc. Natl. Acad. Sci. U.S.A. 87:3640-3644(1990) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• 5alpha-reductases in human physiology: an unfolding story.

  Traish A.M.

  <h4>Objective</h4>5α-reductases are a family of isozymes expressed in a wide host of tissues including the central nervous system (CNS) and play a pivotal role in male sexual differentiation, development and physiology.<h4>Methods</h4>A comprehensive literature search from 1970 to 2011 was made th ... >> More

  <h4>Objective</h4>5α-reductases are a family of isozymes expressed in a wide host of tissues including the central nervous system (CNS) and play a pivotal role in male sexual differentiation, development and physiology.<h4>Methods</h4>A comprehensive literature search from 1970 to 2011 was made through PubMed and the relevant information was summarized.<h4>Results</h4>5α reductases convert testosterone, progesterone, deoxycorticosterone, aldosterone and corticosterone into their respective 5α-dihydro-derivatives, which serve as substrates for 3α-hydroxysteroid dehydrogenase enzymes. The latter transforms these 5α-reduced metabolites into a subclass of neuroactive steroid hormones with distinct physiological functions. The neuroactive steroid hormones modulate a multitude of functions in human physiology encompassing regulation of sexual differentiation, neuroprotection, memory enhancement, anxiety, sleep and stress, among others. In addition, 5α -reductase type 3 is also implicated in the N-glycosylation of proteins via formation of dolichol phosphate. The family of 5α-reductases was targeted for drug development to treat pathophysiological conditions, such as benign prostatic hyperplasia and androgenetic alopecia. While the clinical use of 5α-reductase inhibitors was well established, the scope and the magnitude of the adverse side effects of such drugs, especially on the CNS, is still unrecognized due to lack of knowledge of the various physiological functions of this family of enzymes, especially in the CNS.<h4>Conclusion</h4>There is an urgent need to better understand the function of 5α-reductases and the role of neuroactive steroids in human physiology in order to minimize the potential adverse side effects of inhibitors targeting 5α-reductases to treat benign prostatic hyperplasia and androgenic alopecia. << Less

  Endocr Pract 18:965-975(2012) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.