Substrate Specificity, Gene Structure, and Tissue-specific Distribution of Multiple Human 3α-Hydroxysteroid Dehydrogenases

Abstract

We have expressed in Escherichia coli functionally active proteins encoded by two human cDNAs that were isolated previously by using rat 3 alpha-hydroxysteroid dehydrogenase cDNA as the probe. The expressed proteins catalyzed the interconversion between 5 alpha-dihydrotestosterone and 5 alpha-androstane-3 alpha,17 beta-diol. Therefore, we name these two enzymes type I and type II 3 alpha-hydroxysteroid dehydrogenases. The type I enzyme has a high affinity for dihydrotestosterone, whereas the type II enzyme has a low affinity for the substrate. The tissue-specific distribution of these two enzymes was determined by reverse transcription polymerase chain reaction using gene-specific oligonucleotide primers. The mRNA transcript of the type I enzyme was found only in the liver, whereas that of the type II enzyme appeared in the brain, kidney, liver, lung, placenta, and testis. The structure and sequence of the genes encoding these two 3 alpha-hydroxysteroid dehydrogenases were determined by analysis of genomic clones that were isolated from a lambda EMBL3 SP6/T7 library. The genes coding for the type I and type II enzymes were found to span approximately 20 and 16 kilobase pairs, respectively, and to consist of 9 exons of the same sizes and boundaries. The exons range in size from 77 to 223 base pairs (bp), whereas the introns range in size from 375 bp to approximately 6 kilobase pairs. The type I gene contains a TATA box that is located 27 bp upstream of multiple transcription start sites. In contrast, the type II gene contains two tandem AP2 sequences juxtaposed to a single transcription start site.

Close kinship of human 20α‐hydroxysteroid dehydrogenase gene with three aldo‐keto reductase genes

“…Our PGFS and DD4 genes seemed to be almost the same as those of 3a-HSD type 2 and type 1 genes (Khanna et al 1995b), respectively. Second, the high-stringency RT-PCR with genespeci®c primers made it possible to discriminate each AKR mRNA precisely from the others.…”

“…This 323 amino acid residue-protein has 80% and 69% amino acid identity to rabbit and rat 20a-HSDs, respectively. Surprisingly, it has a much higher amino acid identity to other human liver AKRs: 98% to bile acid-binding protein (BABP)/DD2 [AKR 1C2] ; 88% to prostaglandin F synthase (PGFS)/3a-HSD type 2 [AKR 1C3] (Khanna et al 1995b;Nagase et al 1995;Suzuki-Yamamoto et al 1999); and 83% to DD4/chlordecone reductase/3a-HSD type 1 [AKR 1C4] (Winters et al 1990;Qin et al 1993;Deyashiki et al 1994). Due to the extremely high homology among these AKR members, cDNA probes and antibodies can hardly discriminate 20a-HSD from the others by Northern and Western blot analyses.…”

“…The location of their primers on their genes are also indicated. The primer designs were based on nucleotide sequences appearing in the quoted references (Qin et al 1994;Lou et al 1994;Khanna et al 1995b), the structure and function of the 20a-HSD gene remained to be studied. To investigate human 20a-HSD gene expression in the female reproductive system, we isolated genomic clones harbouring a human 20a-HSD gene, as well as the BABP, PGFS and DD4 genes, identi®ed them by high-stringency polymerase chain reaction (PCR) with gene-speci®c primers, and clari®ed their exon-intron organizations.…”

Preferential expression of hPGFS in primary SCCHN and tumour cell lines derived from respiratory and digestive organs

“…Although the biological function of KIAA0119 is not clear, its biochemical function might serve as a steroid dehydrogenase. The deduced amino-acid sequence was identical to that of AKR1C3, except for two amino acids (Khanna et al, 1995). The enzymatic study demonstrated that the natural substrates of hPGFS were PGD2 and PGF2, but not steroid hormones such as dihydrotestosterone, catalysed by AKR1C3 (Suzuki-Yamamoto et al, 1999).…”

The other side of progestins: effects in the brain

“…Apart from steroid 5α-reductase isozyme family (e.g., SRD5A1, SRD5A2, and SRD5A3) (Azzouni et al 2012), all the remaining enzymes involved in the two-step reduction process in humans belong to the aldo-keto reductase (AKR) superfamily. This includes steroid 5β-reductase or AKR1D1 (Di Costanzo et al 2008, Chen et al 2011 and AKR1C enzymes: AKR1C1 (20α,(3α)-hydroxysteroid dehydrogenase (HSD)) (Hara et al 1996), AKR1C2 (type 3, 3α-HSD) (Deyashiki et al 1994, Dufort et al 1996, AKR1C3 (type 2, 3α-HSD and type 5, 17β-HSD) (Khanna et al 1995), and AKR1C4 (type 1, 3α-HSD) (Penning et al 2000). These enzymes are promiscuous since they can catalyze 3-keto-and also 20-keto-and 17-keto-steroid reduction and are generally expressed in different tissues with the exception of AKR1C4, which is highly liver specific (Penning et al 2000).…”