The mammalian homolog of the frog type II selenodeiodinase does not encode a functional enzyme in the rat
UMass Chan Affiliations
Program in Molecular MedicineDepartment of Medicine, Division of Endocrinology & Metabolism
Department of Physiology
Molecular Endocrinology Laboratories
Document Type
Journal ArticlePublication Date
1999-04-28Keywords
Adipose Tissue, BrownAnimals
Astrocytes
Astrocytoma
Blotting, Western
Bucladesine
Cloning, Molecular
DNA, Complementary
Gene Expression
Immunohistochemistry
Immunosorbent Techniques
Iodide Peroxidase
Protein Biosynthesis
RNA, Messenger
Rats
Transfection
Tumor Cells, Cultured
Xenopus laevis
Life Sciences
Medicine and Health Sciences
Metadata
Show full item recordAbstract
Type II iodothyronine deiodinase is a short-lived, membrane-bound enzyme found in rat brain, brown adipose tissue, and cAMP-stimulated astrocytes. Recently, a full-length complementary DNA (cDNA) encoding a 30-kDa, type II-like selenodeiodinase was cloned from frog, and a homologous partial cDNA (rBAT 1.1), containing two in-frame selenocysteine codons (UGA), was isolated from rat brown adipose tissue. Importantly, the rBAT 1.1 cDNA was derived from a 7.5-kb messenger RNA (mRNA) and did not encode a functional selenoenzyne unless an enabling selenocysteine insertion sequence was appended to the presumed coding region and this cDNA. In this study we determined whether the native 7.5-kb SeD2 mRNA in rat tissues programmed the synthesis of the native type II deiodinase using specific antibodies that were raised against the C-terminus of full-length, 30-kDa SeD2 protein and against the catalytic core of SeD2. Direct analysis of the translation products programmed by the native SeD2 mRNA in cAMP-stimulated astrocytes was performed using antisense deoxynucleotides and hybrid selection strategies. (Bu)2cAMP-stimulated rat astrocytes expressed both type II deiodinase activity (approximately 2500 U/mg protein) and contained abundant levels of the 7.5-kb SeD2 mRNA. However, no immunoreactive 30-kDa SeD2 protein was identified by Western analysis, immunoprecipitation, or immunocytochemistry, and the specific C-terminus antiserum failed to immunoprecipitate deiodinase activity from (Bu)2cAMP-stimulated astrocytes, brown adipose tissue or brain. Instead, the native 7.5-kb SeD2 mRNA encoded a 15-kDa protein that terminated at the first UGA codon and contained the catalytically inactive, N-terminal 129 amino acids of SeD2. These data show that the native 7.5-kb SeD2 mRNA in stimulated astrocytes does not encode D2.Source
Endocrinology. 1999 May;140(5):2206-15.