Isolation, characterization and expression of 11beta-hydroxysteroid dehydrogenase type 2 cDNAs from the testes of Japanese eel (Anguilla japonica) and Nile tilapia (Oreochromis niloticus)

Abstract

The Japanese eel (Anguilla japonica) and Nile tilapia (Oreochromis niloticus) 11 -hydroxysteroid dehydrogenase type 2 (11 -HSD2) cDNAs were isolated from their respective testes cDNA libraries. The cDNAs predict two peptides of 436 and 406 amino acid residues that share about 42% homology with mammalian 11 -HSD type 2 proteins. Analysis of the tissue distribution pattern by RT-PCR reveals that 11 -HSD2 is expressed in a wide variety of tissues in tilapia, with higher expression in kidney and gill of both sexes, and with the highest expression in testis. 11 -Dehydrogenase activity of the eel 11 -HSD2 was confirmed by demonstrating the conversion of cortisol to cortisone by the recombinant protein after transient expression of this cDNA clone in COS-1 cells. Bands of ∼2·7 and ∼3·8 Kb were detected in Northern blot of eel and tilapia testes respectively, which is consistent with the cloned cDNA sizes of the two species. Northern blot analysis also revealed that the expression of the eel testis 11 -HSD2 gene could be induced by human chorionic gonadotropin (hCG) injection, implying a role of 11 -HSD2 in hCG-induced 11-ketotestosterone production and spermatogenesis in the Japanese eel.

Molecular approaches related to the European eel (Anguilla anguilla) reproductive process

“…In the Japanese eel, 11β-HSD mRNA transcripts were not found in immature eel testis, but appeared at day 1, and peaked at day 3 after the administering of hCG injections. Thereafter, the levels decreased rapidly from day 6, and fell very low after day 12 (Jiang et al, 2003). As aforementioned, the difference could be that maturation of the Japanese eel was induced using a single injection, while we applied weekly hCG injections.…”

“…5). The convertion of T into 11-KT can be brought about by the actions of two enzymes, 11β-hydroxylase (cytochrome P450-11β) and 11β-hydroxysteroid dehydrogenase (11β-HSD; Jiang et al, 2003). The enzyme P450-11β metabolizes T into 11β-hydroxytestosterone, the substrate for the production of 11-KT, and the enzyme 11β-HSD metabolizes the 11β-hydroxytestosterone into 11-KT, and cortisol into cortisone.…”

“…Regarding androgens, 11-ketotestosterone (11-KT) is considered to be the most important in teleosts (Miura and Miura, 2003a) and is biosynthesised from testosterone (T) by two enzymes, 11β-hydroxylase (cytochrome P450-11β) and 11β-hydroxysteroid dehydrogenase (11β-HSD; Jiang et al, 2003). In teleosts, 11β-HSD sequence is similar to mammalian 11β-HSD type 2 (Albiston et al, 1994).…”

“…Some examples can be found in the rainbow trout (Oncorhynchus mykiss, Kusakabe et al, 2003), tilapia (Oreochromis niloticus) and Japanese eel (Jiang et al, 2003). In eel, two homologous genes of mammalian 11β-HSD type 2 are present in the testis: 11β-HSD (Albiston et al, 1994;Jiang et al, 2003;Kusakabe et al, 2003) and 11β-HSD short form (11β-HSDsf) , both enzymes with 11β-dehydrogenase activity.…”

“…Teleost 11β-HSD sequences (Kusakabe et al, 2003: Oncorhynchus mykiss; Jiang et al, 2003: Japanese eel) are similar to mammalian 11β-HSD type 2 (Albiston et al, 1994). In eel, two homologous of mammalian 11β-HSD type 2 are present in the testis: 11β-HSD and 11β-HSD short form (11β-HSDsf) (Albiston et al, 1994;Jiang et al, 2003;Kusakabe et al, 2003;Ozaki et al, 2006).11β-HSDsf seems to be the major/main enzyme in the conversion of 11β-hydroxytestosterone (11β-OHT) into 11- KT (Ozaki et al, 2006), while 11β-HSD mainly converts cortisol into cortisone (Jiang et al, 2003).In male fish, the progestins: 17,20β, are the maturation-inducing steroids (MIS), and mediate the process of sperm maturation and spermiation . Nevertheless, DHP has also been proposed to be an essential factor for meiosis initiation, at the beginning of spermatogenesis .…”