Evidence that type III iodothyronine deiodinase in rat astrocyte is a selenoprotein.
A type III iodothyronine deiodinase (D-III) that inactivates thyroid hormones has been recently cloned and identified as a selenoprotein in neonatal rat skin. However, selenium (Se) deficiency does not affect the D-III activity in the rat placenta and decreases the D-III in the rat brain only slightly. This study examines the effect of Se on the D-III activity in cultures of rat brain astrocytes. Astrocytes were depleted in Se by maintaining them in Se-free chemically defined medium for 7 days. These conditions decreased the activity of a recognized selenoprotein, glutathione peroxidase, 3-10-fold. D-III activity induced by 12-0-tetradecanoylphorbol-13-acetate (TPA) was also decreased 2-6-fold. Addition of 30 nM Se to the culture medium caused a rapid increase in TPA-induced D-III activity visible within 1 h. This Se effect was maximal at 3 h (4-fold increase) and dose-dependent. Se also increased the induction of D-III by acidic Fibroblast Growth Factor, 8-bromo-cAMP, T4, or retinoic acid. Cycloheximide blocked the effect of Se on TPA-induced D-III activity, whereas actinomycin D did not. Thus the rapid effect of Se does not require messenger RNA synthesis but requires protein synthesis. We conclude that the D-III in astrocytes is probably a selenoprotein.
Ramauge
M
M
U. 96 INSERM - Unité de Recherche sur la Glande Thyroïde et la Régulation Hormonale, Le Kremlin-Bicêtre Cedex, France.
Pallud
S
S
Esfandiari
A
A
Gavaret
J
J
Lennon
A
A
Pierre
M
M
Courtin
F
F
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000201:enzymology*; D001921:Brain / Q000201:enzymology*; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005260:Female; D016220:Fibroblast Growth Factor 1 / Q000494:pharmacology; D005979:Glutathione Peroxidase / Q000378:metabolism; D007453:Iodide Peroxidase / Q000096:biosynthesis / Q000378:metabolism*; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism*; D007700:Kinetics; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012643:Selenium / Q000494:pharmacology; D051140:Selenoproteins; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013974:Thyroxine / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology
D007527:Isoenzymes; D011506:Proteins; D051140:Selenoproteins; D016220:Fibroblast Growth Factor 1; D003609:Dactinomycin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D014212:Tretinoin; D003513:Cycloheximide; D007453:Iodide Peroxidase; D005979:Glutathione Peroxidase; D012643:Selenium; D013755:Tetradecanoylphorbol Acetate; D013974:Thyroxine