Cloning and characterization of the thyroid iodide transporter

• Published in: Nature (London) Vol. 379; no. 6564; pp. 458 - 460
• Main Authors: Dai, Ge, Levy, Orlie, Carrasco, Nancy
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 01-02-1996; Nature Publishing Group
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Binding and carrier proteins; Biological and medical sciences; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Line; Cloning; Cloning, Molecular; Deoxyribonucleic acid; DNA; DNA, Complementary; Fundamental and applied biological sciences. Psychology; Hormones; Iodides; Membrane Proteins - genetics; Membrane Proteins - metabolism; Molecular Sequence Data; Perchlorate; Proteins; Symporters; Thyroid; Thyroid gland; Thyroid Gland - metabolism; Xenopus laevis; Membrane protein; Heterologous system; Iodides; Rat; Nucleotide sequence; Intrinsic protein; Biological transport; Xenopus laevis; Rodentia; Amphibia; Salientia; Thyroid gland; Gene expression; Vertebrata; Cell line; Mammalia; Complementary DNA; Molecular cloning; Oocyte; Aminoacid sequence; Structural analysis
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/379458a0

Iodide (I-) is an essential constituent of the thyroid hormones T3 and T4, and is accumulated by the thyroid. The transport of iodide, the first step in thyroid hormogenesis, is catalysed by the Na+/I- symporter, an intrinsic membrane protein that is crucial for the evaluation, diagnosis and treatment of thyroid disorders. Although several other important thyroid proteins involved in hormogenesis have been characterized, the Na+/I- symporter has not. Here we report the isolation of a complementary DNA clone that encodes this symporter, as a result of functional screening of a cDNA library from a rat thyroid-derived cell line (FRTL-5) in Xenopus laevis oocytes. Oocyte microinjection of an RNA transcript made in vitro from this cDNA clone elicited a more than 700-fold increase in perchlorate-sensitive Na+/I- symport activity over background. To our knowledge, this is the first iodide-transporting molecule to have its cDNA cloned, providing a missing link in the thyroid hormone biosynthetic pathway.