Differential androgen and estrogen substrates specificity in the mouse and primates type 12 17β-hydroxysteroid dehydrogenase

Abstract

Recently, we have shown that human and monkey type 12 17b-hydroxysteroid dehydrogenases (17b-HSD12) are estrogen-specific enzymes catalyzing the transformation of estrone (E 1 ) into estradiol (E 2 ). To further characterize this novel steroidogenic enzyme in an animal model, we have isolated a cDNA fragment encoding mouse 17b-HSD12 and characterized its enzymatic activity. Using human embryonic kidney cells (HEK)-293 cells stably expressing mouse 17b-HSD12, we found that in contrast with the human and monkey enzymes, which are specific for the transformation of E 1 to E 2 , mouse 17b-HSD12 also catalyzes the transformation of 4-androstenedione into testosterone (T), dehydroepiandrosterone (DHEA) into 5-androstene-3b,17b-diol (5-diol), as well as androsterone into 5a-androstane-3a,17b-diol (3a-diol). Previously, we have shown that the specificity of human and monkey 17b-HSD12s for C18-steroid is due to the presence of a bulky phenylalanine (F) at position 234 creating steric hindrance, preventing the entrance of C19-steroids into the active site. To determine whether the smaller size of the corresponding leucine (L) in the mouse sequence is responsible for the entrance of androgenic substrates, we performed site-directed mutagenesis to substitute Leu 234 for Phe in the mouse enzyme. In agreement with our hypothesis, the mutated enzyme has a highly reduced ability to metabolize androgens. mRNA quantification in several mouse tissues using real-time PCR shows that mouse 17b-HSD12 mRNA is highly expressed in the female clitoral gland, male preputial gland, as well as in retroperitoneal fat and adrenal of both sexes. The differential androgenic/estrogenic substrate specificity of type 12 17b-HSD in the mouse and primates seems to agree with the observation that androgen and estrogen in the mouse are provided almost exclusively by gonads, while in primates an important part of these steroid hormones are produced locally from adrenal precursors.

Caenorhabditis elegans LET-767 is able to metabolize androgens and estrogens and likely shares common ancestor with human types 3 and 12 17β-hydroxysteroid dehydrogenases

“…On the other hand, in the presence of the cDNA insert encoding let-767, high conversion of 4-androstenedione into testosterone and estrone into estradiol has been observed, thus indicating that LET-767 is able to convert androgen as well as estrogen substrates. The situation is similar to that observed with the mouse 17b-HSD12 (Blanchard & Luu-The 2007) that possesses a small size amino acid (L) at position 234. In human, 17b-HSD12 (Luu-The et al 2006) has lost the ability to metabolize androgen that is produced by the isoform 17b-HSD3 (Geissler et al 1994).…”

“…However, in contrast with the human enzymes that show substrate specificity, LET-767 catalyzes the transformation of 4-androstenedione into testosterone as well as estrone into estradiol, similar to that found in the mouse 17b-HSD12 (Blanchard & Luu-The 2007). Previously, we have shown that the amino acid F234 is responsible, in part, for the androgenic-estrogenic substrate specificity.…”

“…Both genes have, however, evolved to acquire different substrate selectivity, androgen for 17b-HSD3 and estrogen for 17b-HSD12 in human and primates (Luu-The et al 2006, Liu et al 2007. It is noteworthy that mouse 17b-HSD12 catalyzes the transformation of both androgens and estrogens (Blanchard & Luu-The 2007). In agreement with their role in the formation of active sex steroid and reproduction in human, 17b-HSD3 is highly expressed in the testis, while 17b-HSD12 is expressed significantly in the ovary and mammary gland (Luu-The et al 2006).…”

“…In human and primates, 17b-HSD3 and 12 diverge and acquire substrate specificity for androgen and estrogen respectively. In the mouse, it is likely that androgen-estrogen selectivity is less critical than in human, since many estrogen-selective 17b-HSDs in human such as 17b-HSD1 and 12 catalyze as well the production of androgens (Nokelainen et al 1996, Blanchard & Luu-The 2007. It is noteworthy that 17b-HSD3 is responsible for the formation of testosterone, one of the key steroid hormones.…”

The diversity of sex steroid action: novel functions of hydroxysteroid (17β) dehydrogenases as revealed by genetically modified mouse models

“…In humans, the highest expression of HSD17B12 is detected in the tissues involved in lipid metabolism, including the liver, kidney and muscle (Sakurai et al 2006). In mice, the expression has also been detected in the brown and white adipose tissue (Moon & Horton 2003, Sakurai et al 2006, Blanchard & Luu-The 2007. Studies on zebra fish have, furthermore, supported the role of HSD17B12 in fatty acid synthesis (Mindnich et al 2004), and studies with LET-767, the Caenorhabditis elegans ortholog of HSD17B12, have shown that the enzyme is required for the production of branched-chain and longchain fatty acids in vivo (Entchev et al 2008).…”