The Human Type 2 Iodothyronine Deiodinase Is a Selenoprotein Highly Expressed in a Mesothelioma Cell Line

• Published in: The Journal of biological chemistry Vol. 276; no. 32; pp. 30183 - 30187
• Main Authors: Curcio, C, Baqui, M M, Salvatore, D, Rihn, B H, Mohr, S, Harney, J W, Larsen, P R, Bianco, A C
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 10.08.2001
• Subjects: Acetylcysteine - analogs & derivatives; Acetylcysteine - pharmacology; Animals; D2 protein; hDio2 gene; Humans; Immunohistochemistry; Iodide Peroxidase - biosynthesis; Iodide Peroxidase - chemistry; Iodide Peroxidase - physiology; iodothyronine deiodinase (type 2); Kinetics; mesothelioma; Mesothelioma - enzymology; Microscopy, Confocal; Microscopy, Fluorescence; Propylthiouracil - pharmacology; Proteins - chemistry; Proteins - physiology; RNA, Messenger - metabolism; Selenium - metabolism; Selenoproteins; Transfection; Tumor Cells, Cultured
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.C100325200

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 ∼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 n m , resistance to propylthiouracil, and a short half-life (∼30 min). D2 activity is ∼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 ∼2.5-fold whereas substrate (T 4 ) reduces both D2 activity and 75 Se-p31 ∼2–3-fold. MG132 or lactacystin (10 μ m ), 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.