University of Oulu

Biosynthesis of estradiol : cloning and characterization of rodent 17β-hydroxysteroid dehydrogenase/17-ketosteroid reductase types 1 and 7

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Author: Nokelainen, Pasi1,2
Organizations: 1University of Oulu, Biocenter Oulu
2University of Oulu, Faculty of Medicine, WHO Collaborating Centre for Research on Reproductive Health
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1 MB)
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Language: English
Published: 2000
Publish Date: 2000-08-22
Thesis type: Doctoral Dissertation
Defence Note: Academic Dissertation to be presented with the assent of the Faculty of Medicine, University of Oulu, for public discussion in Auditorium 9 of the University Hospital of Oulu, on September 29th, 2000, at 12 noon.
Reviewer: Professor Heikki Ruskoaho
Professor Timo Ylikomi


17β-Hydroxysteroid dehydrogenases (17HSDs)/17-ketosteroid reductases (17KSRs) modulate the biological activity of certain estrogens and androgens by catalyzing dehydrogenase and reductase reactions between 17β-hydroxy and 17-ketosteroids.

In the present study, cDNAs encoding mouse and rat 17HSD/KSR1 were cloned in order to study the role of rodent type 1 enzyme in ovarian estradiol (E₂) biosynthesis and its enzymatic characteristics. Both rat and mouse 17HSD/KSR1 were expressed in granulosa cells of developing follicles, where diethylstilbestrol and follicle-stimulating hormone stimulated follicular maturation and up-regulated the expression of 17HSD/KSR1, whereas human chorionic gonadotropin caused luteinization of follicles and down-regulation of the enzyme. In line with this, the rodent type 1 enzymes are not expressed in the corpus luteum (CL). Mouse 17HSD/KSR1 showed substrate specificity different from that of the human counterpart. The mouse type 1 enzyme catalyzed the reaction from androstenedione to testosterone at least as efficiently as estrone (E₁) to E₂, while human 17HSD/KSR1 clearly preferred the E₁ to E₂ reaction.

A mouse mammary epithelial cell line was found to possess strong estrogenic 17KSR activity. A novel type of 17HSD/KSR responsible for this activity was expression-cloned on the basis of its ability to convert E₁ to E₂ and it was chronologically named 17HSD/KSR7. Interestingly, it showed 89 % identity with a rat protein called prolactin receptor-associated protein (PRAP), which is expressed in the CL. Enzymatic characterization showed that both mouse 17HSD/KSR7 and PRAP efficiently catalyzed the reaction from E₁ to E₂. The mouse type 7 enzyme was most abundantly expressed in the ovary and placenta. Similar primary structure, enzymatic characteristics, and tissue distribution of mouse 17HSD/KSR7 and PRAP suggest that PRAP is rat 17HSD/KSR7.

Further studies showed that in rat ovaries 17HSD/KSR7 is primarily expressed in the middle and second half of pregnancy, in parallel with E₂ secretion from the CL. Using in situ hybridization, cell-specific expression of 17HSD/KSR7 was studied in the mouse ovary, uterus and placenta. In the mouse ovary, the enzyme was expressed exclusively in the CL. In the uterus on day 5 post coitum (p.c.), the type 7 enzyme was expressed in the decidua, mostly in the inner zone of antimesometrial decidua. Between day 8 and 9 p.c. the enzyme was abundant in decidua capsularis of the developing placenta, after which expression moved to the basal zone. On days 12 and 14 p.c., mouse type 7 enzyme was abundantly expressed in the spongiotrophoblasts, where expression decreased towards parturition. Altogether, rodent 17HSD/KSR7 is a new 17HSD/KSR which is involved in the biosynthesis of E₂ in the ovaries. In addition, E₂ produced locally in the decidua and placenta by the type 7 enzyme may have a role in decidualization and/or implantation and placentation.

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Series: Acta Universitatis Ouluensis. D, Medica
ISSN-E: 1796-2234
ISBN: 951-42-5751-0
ISBN Print: 951-42-5750-2
Issue: 607
Copyright information: © University of Oulu, 2000. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.