The human type 2 iodothyronine deiodinase is a selenoprotein highly expressed in a mesothelioma cell line.
Types 1 and 3 iodothyronine deiodinases are known to be selenocysteine-containing enzymes. Although a putative human type 2 iodothyronine deiodinase (D2) gene (hDio2) encoding a similar selenoprotein has been identified, basal D2 activity is not selenium (Se)-dependent nor has D2 been labeled with (75)Se. A human mesothelioma cell line (MSTO-211H) has recently been shown to have approximately 40-fold higher levels of hDio2 mRNA than mesothelial cells. Mesothelioma cell lysates activate thyroxine (T(4)) to 3,5,3'-triiodothyronine with typical characteristics of D2 such as low K(m) (T(4)), 1.3 nm, resistance to propylthiouracil, and a short half-life ( approximately 30 min). D2 activity is approximately 30-fold higher in Se-supplemented than in Se-depleted medium. An antiserum prepared against a peptide deduced from the Dio2 mRNA sequence precipitates a (75)Se protein of the predicted 31-kDa size from (75)Se-labeled mesothelioma cells. Bromoadenosine 3'5' cyclic monophosphate increases D2 activity and (75)Se-p31 approximately 2.5-fold whereas substrate (T(4)) reduces both D2 activity and (75)Se-p31 approximately 2-3-fold. MG132 or lactacystin (10 microm), inhibitors of the proteasome pathway by which D2 is degraded, increase both D2 activity and (75)Se-p31 3-4-fold and prevent the loss of D2 activity during cycloheximide or substrate (T(4)) exposure. Immunocytochemical studies with affinity-purified anti-hD2 antibody show a Se-dependent increase in immunofluorescence. Thus, human D2 is encoded by hDio2 and is a member of the selenodeiodinase family accounting for its highly catalytic efficiency in T(4) activation.
Curcio
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Department of Medicine, Thyroid Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Baqui
M M
MM
Salvatore
D
D
Rihn
B H
BH
Mohr
S
S
Harney
J W
JW
Larsen
P R
PR
Bianco
A C
AC
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D006801:Humans; D007150:Immunohistochemistry; D007453:Iodide Peroxidase / Q000096:biosynthesis* / Q000737:chemistry / Q000502:physiology*; D007700:Kinetics; D008654:Mesothelioma / Q000201:enzymology*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D011441:Propylthiouracil / Q000494:pharmacology; D011506:Proteins / Q000737:chemistry* / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D012643:Selenium / Q000378:metabolism; D051140:Selenoproteins; D014162:Transfection; D014407:Tumor Cells, Cultured
D011506:Proteins; D012333:RNA, Messenger; D051140:Selenoproteins; C067713:lactacystin; D011441:Propylthiouracil; D007453:Iodide Peroxidase; D012643:Selenium; D000111:Acetylcysteine