5Alpha-reductase type 2 and androgen receptor expression in gonadotropin releasing hormone GT1-1 cells.
Gonadal steroids are potent modulators of gonadotropin releasing hormone (GnRH) secretion, and androgen binding sites and 5alpha-reductase activity have been found in the immortalized GnRH secreting cell line GT1-1, suggesting the existence of a direct androgenic control of GnRH dynamics. Two isoforms of the 5alpha-reductase have been cloned with very different biochemical/functional properties: 5alpha-reductase type 1 (widely distributed in the body) and 5alpha-reductase type 2 (confined in androgen target structures). We have analysed whether, in GT1-1, androgen binding sites are linked to "classical" androgen receptor, and which 5alpha-reductase isoform is active. Reverse transcriptase-polymerase chain reaction analysis showed that the mRNAs coding for androgen receptor and for the two 5alpha-reductase isoforms are all expressed in GT1-1 cells. However, the 5alpha-reductase enzymatic reaction showed a peak of activity at a narrow pH around 5.5, the optimum for the 5alpha-reductase type 2. The affinity for testosterone, of the enzyme present in GT1-1 cells, was very similar to that observed for the recombinant type 2 isozyme expressed in yeasts. The data indicate that GT1-1 cells (i) express a "classical" androgen receptor and (ii) contain the 5alpha-reductase type 2 isoform, a specific marker of androgen-responsiveness.
Poletti
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Istituto di Endocrinologia, Università di Milano, via Balzaretti 2, 20133 Milan, Italy. angelo.poletti@unimi.it
Rampoldi
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Piccioni
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Volpi
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Simeoni
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Zanisi
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Martini
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D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D002460:Cell Line; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D011944:Receptors, Androgen / Q000096:biosynthesis* / Q000235:genetics; D013379:Substrate Specificity; D013739:Testosterone / Q000378:metabolism
D007527:Isoenzymes; D012333:RNA, Messenger; D011944:Receptors, Androgen; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase